Old Irish

Old Irish
Pronunciation [ˈɡoːi̯ðʲelɡ]
Region Ireland, Isle of Man, western coast of Great Britain
Era 6th century–10th century; evolved into Middle Irish about the 10th century
Early forms
Primitive Irish
  • Old Irish
Language codes
ISO 639-2 sga
ISO 639-3 sga
Glottolog oldi1245[1]
Linguasphere 50-AAA-ad

Old Irish (Old Irish: Goídelc, Irish: Sean-Ghaeilge) (sometimes called Old Gaelic[2][3]) is the name given to the oldest form of the Goidelic languages for which extensive written texts are extant. It was used from c. AD 600–900. The primary contemporary texts are dated c. AD 700–850; by AD 900 the language had already transitioned into early Middle Irish. Some Old Irish texts date from the 10th century, although these are presumably copies of texts composed at an earlier time period. Old Irish is thus the ancestor of Modern Irish, Manx, and Scottish Gaelic.[2]

Old Irish is known for having a particularly complex system of morphology and especially of allomorphy (more or less unpredictable variations in stems and suffixes in differing circumstances) as well as a complex sound system involving grammatically significant consonant mutations to the initial consonant of a word. Initial consonant mutation must have been present in at least late Common Celtic (Proto-Celtic) because this distinguishing feature has survived with grammatical significance in both modern Welsh and Breton, and the extinct Cornish language also featured. Because the languages belong to the Brittonic branch of the Celtic language group (so-called "P-Celtic"), initial mutation must predate the split in the development paths of the Brittonic and Goidelic languages. No mutations are, however, attested in Gaulish material so a parallel evolution of the phenomenon in the neo-Celtic languages is also possible. Much of the complex allomorphy has been lost, but the rich sound system has been maintained, with little change, in the modern languages.

Contemporary Old Irish scholarship is still greatly influenced by the works of a small number of scholars active in the late 19th and early 20th centuries such as Rudolf Thurneysen (1857–1940) and Osborn Bergin (1873–1950).

Notable characteristics

Notable characteristics of Old Irish compared with other old Indo-European languages, are:

Old Irish also preserves most aspects of the complicated Proto-Indo-European (PIE) system of morphology. Nouns and adjectives are declined in three genders (masculine, feminine, neuter); three numbers (singular, dual, plural); and five cases (nominative, vocative, accusative, dative and genitive). Most PIE noun stem classes are maintained (o-, yo-, ā-, -, i-, u-, r-, n-, s-, and consonant stems). Most of the complexities of PIE verbal conjugation are also maintained, and there are new complexities introduced by various sound changes (see below).


Old Irish was the only member of the Goidelic/Gaelic branch of the Celtic languages, which is, in turn, a subfamily of the wider Indo-European language family that also includes the Slavonic, Italic/Romance, Indo-Aryan and Germanic subfamilies, along with several others. Old Irish is the ancestor of all modern Goidelic languages: Modern Irish, Scottish Gaelic and Manx.

A still older form of Irish is known as Primitive Irish. Fragments of Primitive Irish, mainly personal names, are known from inscriptions on stone written in the Ogham alphabet. The inscriptions date from about the 4th to the 6th centuries. Primitive Irish appears to have been very close to Common Celtic, the ancestor of all Celtic languages, and it had a lot of the characteristics of other archaic Indo-European languages.


Relatively little survives in the way of strictly contemporary sources. They are represented mainly by shorter or longer glosses on the margins or between the lines of religious Latin manuscripts, most of them preserved in monasteries in Germany, Italy, Switzerland, France and Austria, having been taken there by early Irish missionaries. Whereas in Ireland, many of the older manuscripts appear to have been worn out through extended and heavy use, their counterparts on the Continent were much less prone to the same risk because once they ceased to be understood, they were rarely consulted.[4]

The earliest Old Irish passages may be the transcripts found in the Cambrai Homily, which is thought to belong to the early 8th century. The Book of Armagh contains texts from the early 9th century. Important Continental collections of glosses from the 8th and 9th century include the Würzburg Glosses (mainly) on the Pauline Epistles, the Milan Glosses on a commentary to the Psalms and the St Gall Glosses on Priscian's Grammar.

Further examples are found at Karlsruhe (Germany), Paris (France), Milan, Florence and Turin (Italy). A late 9th-century manuscript from the abbey at Reichenau, now in St. Paul in Carinthia (Austria), contains a spell and four Old Irish poems. The Liber Hymnorum and the Stowe Missal date from about 900 to 1050.

In addition to contemporary witnesses, the vast majority of Old Irish texts are attested in manuscripts of a variety of later dates. Manuscripts of the later Middle Irish period, such as the Lebor na hUidre and the Book of Leinster, contain texts, which are thought to derive from written exemplars in Old Irish now lost and retain enough of their original form to merit classification as Old Irish.

The preservation of certain linguistic forms current in the Old Irish period may provide reason to assume that an Old Irish original directly or indirectly underlies the transmitted text or texts.



The consonant inventory of Old Irish is shown in the chart below. The complexity of Old Irish phonology is from a four-way split of phonemes inherited from Primitive Irish, with both a fortis–lenis and a "broad–slender" (velarised vs. palatalised) distinction arising from historical changes. The sounds /f v θ ð x ɣ h ṽ n l r/ are the broad lenis equivalents of broad fortis /p b t d k ɡ s m N L R/; likewise for the slender (palatalised) equivalents. (However, most /f fʲ/ sounds actually derive historically from /w/.)

Labial Dental Alveolar Velar Glottal
Nasal broad m N  n ŋ
slender    ŋʲ
Plosive broad p  b t  d k  ɡ
slender         ɡʲ
Fricative broad f  v θ  ð s x  ɣ h
slender    θʲ  ðʲ   ɣʲ
slender ṽʲ
Approximant broad R  r
Lateral broad L  l

Some details of Old Irish phonetics are not known. /sʲ/ may have been pronounced [ɕ] or [ʃ], as in Modern Irish. /hʲ/ may have been the same sound as /h/ or /xʲ/. The precise articulation of the fortis sonorants /N/, /Nʲ/, /L/, /Lʲ/, /R/, /Rʲ/ is unknown, but they were probably longer, tenser and generally more strongly articulated than their lenis counterparts /n/, /nʲ/, /l/, /lʲ/, /r/, /rʲ/, as in the Modern Irish dialects (Connacht Irish) that still possess a four-way distinction in the coronal nasals and laterals. /Nʲ/ and /Lʲ/ may have been pronounced [ɲ] and [ʎ] respectively. The difference between /R(ʲ)/ and /r(ʲ)/ may have been that the former were trills while the latter were flaps.


Old Irish had distinctive vowel length in both monophthongs and diphthongs. Short diphthongs were monomoraic, taking up the same amount of time as short vowels, while long diphthongs were bimoraic, the same as long vowels. (This is much like the situation in Old English but different from Ancient Greek whose shorter and longer diphthongs were bimoraic and trimoraic, respectively: /ai/ vs. /aːi/.) The inventory of Old Irish long vowels changed significantly over the Old Irish period, but the short vowels changed much less.

The following short vowels existed:

Monophthongs Diphthongs
Close i u ĭu
Mid e o ĕu (ŏu)1
Open a ău

1The short diphthong ŏu may have existed very early in the Old Irish period/but not later on.

Archaic Old Irish (before about AD 750) had the following inventory of long vowels:

Monophthongs Diphthongs
Close iu ui
Mid e₁ː, e₂ː1 o₁ː, (o₂ː?)2 eu oi, (ou)3
Open ai, au3

1Both /e₁ː/ and /e₂ː/ were normally written é but must have been pronounced differently because they have different origins and distinct outcomes in later Old Irish. /e₁ː/ stems from Proto-Celtic *ē (< PIE *ei), or from ē in words borrowed from Latin. e₂ː generally stems from compensatory lengthening of short *e because of loss of the following consonant (in certain clusters) or a directly following vowel in hiatus. It is generally thought that /e₁ː/ was higher than /e₂ː/.[5] Perhaps /e₁ː/ was [eː] while /e₂ː/ was [ɛː]. They are clearly distinguished in later Old Irish, in which /e₁ː/ becomes ía (but é before a palatal consonant). /e₂ː/ becomes é in all circumstances. Furthermore, /e₂ː/ is subject to u-affection, becoming éu or íu, while /e₁ː/ is not.

2A similar distinction may have existed between /o₁ː/ and /o₂ː/, both written ó, and stemming respectively from former diphthongs (*eu, *au, *ou) and from compensatory lengthening. However, in later Old Irish both sounds appear usually as úa, sometimes as ó, and it is unclear whether /o₂ː/ existed as a separate sound any time in the Old Irish period.

3/ou/ existed only in early archaic Old Irish (c. AD 700 or earlier); afterwards it merged into /au/. Neither sound occurred before another consonant, and both sounds became ó in later Old Irish (often ú or u before another vowel). The late ó does not develop into úa, suggesting that áu > ó postdated ó > úa.

Later Old Irish had the following inventory of long vowels:

Monophthongs Diphthongs
Close iu, ia ui, ua
Mid eu oi?1

1Early Old Irish /ai/ and /oi/ merged in later Old Irish. It is unclear what the resulting sound was, as scribes continued to use both and to indicate the merged sound. The choice of /oi/ in the table above is somewhat arbitrary.

The distribution of short vowels in unstressed syllables is a little complicated. All short vowels may appear in absolutely final position (at the very end of a word) after both broad and slender consonants. The front vowels /e/ and /i/ are often spelled ae and ai after broad consonants, which might indicate a retracted pronunciation here, perhaps something like [ɘ] and [ɨ]. All ten possibilities are shown in the following examples:

Old Irish Pronunciation English Annotations
marba /ˈmarva/ kill 1 sg. subj.
léicea /ˈLʲeːɡʲa/ leave 1 sg. subj.
marbae /ˈmarve/ ([ˈmarvɘ]?) kill 2 sg. subj.
léice /ˈLʲeːɡʲe/ leave 2 sg. subj.
marbai /ˈmarvi/ ([ˈmarvɨ]?) kill 2 sg. indic.
léici /ˈlʲeːɡʲi/ leave 2 sg. indic.
súlo /ˈsuːlo/ eye gen.
doirseo /ˈdoRʲsʲo/ door gen.
marbu /ˈmarvu/ kill 1 sg. indic.
léiciu /ˈLʲeːɡʲu/ leave 1 sg. indic.

The distribution of short vowels in unstressed syllables, other than when absolutely final, was quite restricted. It is usually thought that there were only two allowed phonemes: /ǝ/ (written a, ai, e or i depending on the quality of surrounding consonants) and /u/ (written u or o). The phoneme /u/ tended to occur when the following syllable contained an *ū in Proto-Celtic (for example, dligud /ˈdʲlʲiɣuð/ "law" (dat.) < PC *dligedū), or after a broad labial (for example, lebor /ˈLʲevor/ "book"; domun /ˈdoṽun/ "world"). The phoneme /ǝ/ occurred in other circumstances. The occurrence of the two phonemes was generally unrelated to the nature of the corresponding Proto-Celtic vowel, which could be any monophthong: long or short.

Long vowels also occur in unstressed syllables. However, they rarely reflect Proto-Celtic long vowels, which were shortened prior to the deletion (syncope) of inner syllables. Rather, they originate in one of the following ways:


Stress is generally on the first syllable of a word. However, in verbs it occurs on the second syllable when the first syllable is a clitic (the verbal prefix as- in as⋅beir /asˈberʲ/ "he says"). In such cases, the unstressed prefix is indicated in grammatical works with a following centre dot (⋅).


As with most medieval languages, the orthography of Old Irish is not fixed, so the following statements are to be taken as generalisations only. Individual manuscripts may vary greatly from these guidelines.

The Old Irish alphabet consists of the following eighteen letters of the Latin alphabet:

a, b, c, d, e, f, g, h, i, l, m, n, o, p, r, s, t, u

In addition, the acute accent and the superdot are used as diacritics with certain letters:

Some digraphs are also used:

The letter i is placed after a vowel letter to indicate that the following consonant was palatalised: ai, ei, oi, ui; ái, éi, ói, úi
The letter h is placed after c, t, p to indicate a fricative: ch, th, ph
The diphthongs are also indicated by digraphs: áe/, ía, , áu, óe/, úa, éu, óu, iu, au, eu

The following table indicates the broad pronunciation of various consonant letters in various environments:

Consonant letter Word-initial After a vowel
unmutated nasalised lenited
b /b/ /v/
c /k/ /ɡ/ /k, ɡ/
d /d/ /ð/
f /f/ /v/ silent /f/
g /ɡ/ /ɣ/
h See discussion below
l /L/ /l/
m /m/ /ṽ/
n /N/ /n/
p /p/ /b/ /p, b/
r /R/ /r/
s /s/ /h/ /s/
t /t/ /d/ /t, d/


The slender (palatalised) variants of the above consonants occur in the following environments:

Although Old Irish has both a sound /h/ and a letter h, there is no consistent relationship between the two. Vowel-initial words are sometimes written with an unpronounced h, especially if they are very short (the preposition i "in" was sometimes written hi) or if they need to be emphasised (the name of Ireland, Ériu, was sometimes written Hériu). On the other hand, words that begin with the sound /h/ are usually written without it: a ór /a hoːr/ "her gold". If the sound and the spelling co-occur, it is by coincidence, as ní hed /Nʲiː heð/ "it is not".

After a vowel or l, n, or r the letters c, p, t can stand for either voiced or voiceless stops; they can also be written double with either value:

Old Irish Pronunciation English
mac or macc /mak(k)/ son
bec or becc /bʲeɡ(ɡ)/ small
op or opp /ob(b)/ refuse
brat or bratt /brat(t)/ mantle
brot or brott /brod(d)/ goad
derc /dʲerk/ hole
derc /dʲerɡ/ red
daltae /daLte/ fosterling
celtae /kʲeLde/ who hide
anta /aNta/ of remaining
antae /aNde/ who remain

Geminate consonants appear to have existed at the beginning of the Old Irish period but were simplified by the end, as is generally reflected by the spelling generally although double ll mm nn rr were eventually repurposed to indicate nonlenited variants of those sounds in certain positions.

After a vowel the letters b, d, g stand for the fricatives /v, ð, ɣ/ or their slender equivalents:

Old Irish Pronunciation English
dub /duv/ black
mod /moð/ work
mug /muɣ/ slave
claideb /klaðʲǝv/ sword
claidib /klaðʲǝvʲ/ swords

After m, b is a stop, but after d, l and r, it is a fricative:

Old Irish Pronunciation English
imb /imʲbʲ/ butter
odb /oðv/ knot (in a tree)
delb /dʲelv/ image
marb /marv/ dead

After n and r, d is a stop:

Old Irish Pronunciation English
bind /bʲiNʲdʲ/ melodious
cerd /kʲeRd/ "art, skill"

After n, l, and r, g is usually a stop, but it is a fricative in a few words:

Old Irish Pronunciation English
long /Loŋɡ/ ship
delg or delc /dʲelɡ/ thorn
argat or arggat /arɡ(ɡ)ǝd/ silver
ingen[* 1] /inʲɣʲǝn/ daughter
ingen[* 1] /iNʲɡʲǝn/ nail, claw
bairgen /barʲɣʲǝn/ loaf of bread

After vowels m is usually a fricative, but sometimes a (nasal) stop, in which case it is also often written double:

Old Irish Pronunciation English
dám /daːṽ/ company
lom or lomm /Lom/ bare

The digraphs ch, ph, th do not occur in word-initial position except under lenition, but wherever they occur, they are pronounced /x/, /f/, /θ/.

Old Irish Pronunciation English
ech /ex/ horse
oíph /oif/ beauty
áth /aːθ/ ford

The letters l, n, and r are generally written double when they indicate the tense sonorants, single when they indicate the lax sonorants. Originally, it reflected an actual difference between single and geminate consonants, as tense sonorants in many positions (such as between vowels or word-finally) developed from geminates. As the gemination was lost, the use of written double consonants was repurposed to indicate tense sonorants. Doubly written consonants of this sort do not occur in positions where tense sonorants developed from non-geminated Proto-Celtic sonorants (such as word-initially or before a consonant).

Old Irish Pronunciation English
corr /koR/ crane
cor /kor/ putting
coll /koL/ hazel
col /kol/ sin
sonn /soN/ stake
son /son/ sound
ingen[* 1] /inʲɣʲǝn/ daughter
ingen[* 1] /iNʲɡʲǝn/ nail, claw

Written vowels a, ai, e, i in poststressed syllables (except absolutely word-finally) all seem to represent phonemic /ǝ/. The particular vowel that appears is determined by the quality (broad vs. slender) of the surrounding consonants and has no relation to the etymological vowel quality:

Preceding consonant Following consonant Spelling Example
broad broad a dígal /ˈdʲiːɣǝl/ "vengeance" (nom.)
broad slender (in open syllable) a
broad slender (in closed syllable) ai dígail /ˈdʲiːɣǝlʲ/ "vengeance" (acc./dat.)
slender broad e dliged /ˈdʲlʲiɣʲǝð/ "law" (acc.)
slender slender i dligid /ˈdʲlʲiɣʲǝðʲ/ "law" (gen.)

It seems likely that spelling variations reflected allophonic variations in the pronunciation of /ǝ/.


Old Irish was affected by a series of phonological changes that radically altered its appearance compared with Proto-Celtic and older Celtic languages (such as Gaulish, which still had the appearance of typical early Indo-European languages such as Latin or Ancient Greek). The changes were such that Irish was not recognized as Indo-European at all for much of the 19th century. The changes must have happened quite rapidly, perhaps in only 100 or 200 years around AD 500–600, because almost none of the changes are visible in Primitive Irish (4th to 6th centuries AD), and all of them are already complete in archaic Old Irish (8th century AD). A capsule summary of the most important changes is (in approximate order):[8][9]

  1. Syllable-final *n (from PIE *m, *n) assimilated to the following phoneme, even across word boundaries in the case of syntactically connected words.
    • Voiceless stops became voiced: *mp *nt *nk > /b d ɡ/.
    • Voiced stops became prenasalised /ᵐb, ⁿd, ᵑɡ/. They were reduced to simple nasals during the Old Irish period.
    • Before a vowel, /n-/ was attached to the beginning of the syllable.
  2. Lenition of all single consonants between vowels. That applied across word boundaries in the case of syntactically connected words.
    • Stops became fricatives.
    • *s became /h/ (later lost unless the following syllable was stressed).
    • *w was eventually lost (much later).
    • *m became a nasalised continuant (/w̃/; perhaps [w̃] or [β̃]).
    • *l *n *r remained, but the non-lenited variants were strengthened to /L N R/ (see phonology section above).
  3. Extensive umlaut ("affection") of short vowels, which were raised or lowered to agree with the height of following Proto-Celtic vowels. Similarly, rounding of *a to /o/ or /u/ often occurred adjacent to labial consonants.
  4. Palatalization of all consonants before front vowels.
  5. Loss of part or all of final syllables.
  6. Loss of most interior vowels (syncope).

They led to the following effects:

Examples of changes

The following are some examples of changes between Primitive Irish and Old Irish.

Primitive Irish Old Irish Meaning
inigena[10] ingen daughter
qrimitir[11] cruimther priest
maqqi[12] maicc son (gen.)
velitas[13] filed poet (gen.)
Lugudeccas[14] Luigdech genitive of Lug(u)id (name)
Anavlamattias[15] Anfolmithe genitive of Anblamath (name)
Coillabotas[16] Coílbad genitive of name


These various changes, especially syncope, produced quite complex allomorphy, because the addition of prefixes or various pre-verbal particles (proclitics) in Proto-Celtic changed the syllable containing the stress: According to the Celtic variant of Wackernagel's Law, the stress fell on the second syllable of the verbal complex, including any prefixes and clitics. By the Old Irish period, most of this allomorphy still remained, although it was rapidly eliminated beginning in the Middle Irish period.

Among the most striking changes are in prefixed verbs with or without pre-verbal particles. With a single prefix and without a proclitic, stress falls on the verbal root, which assumes the deuterotonic ("second-stressed") form. With a prefix and also with a proclitic, stress falls on the prefix, and the verb assumes the prototonic ("first-stressed") form. Rather extreme allomorphic differences can result:

Example differences between deuterotonic and prototonic forms of various verbs. Stress falls directly after the center dot or hyphen.[17]
Earlier form Deuterotonic Meaning Prototonic Meaning
*ess-bero(n)t < PIE *-bheronti as·berat /as-ˈbʲerəd/ they say ní-epret /Nʲiː-ˈhebrʲəd/ they do not say
*cum-uss-ana con·osna he rests ní-cumsana he does not rest
*de-ro-uss-scochi do·rósc(a)i he surpasses ní-derscaigi he does not surpass
*de-lugi < PIE *-logheyeti do·lug(a)i he pardons ní-dílg(a)i he does not pardon
*de-ro-gn... do·róna he may do ní-derna he may not do

The following table shows how these forms might have been derived:

Possible derivation of some verbal forms
"they say" "they do not say" "he rests" "he does not rest" "he surpasses" "he does not surpass"
Post-PIE eks bheronti nē eks bheronti kom uks h₂eneh₂ti nē kom uks h₂eneh₂ti dē pro uks skokeyeti nē dē pro uks skokeyeti
Proto-Celtic eks ˈberonti nī ˈeks-beronti kom ˈuks-anāti nī ˈkom-uks-anāti dī ˈɸro-uks-skokīti nī ˈdī-ɸro-uks-skokīti
Early Irish ess-es ˈberont ní-s ˈess-beront kon-es ˈuss-anát ní-s ˈkom-uss-anát dí-s ˈro-uss-skokít ní-s ˈdi-ro-uss-skokít
Nasal assimilation ess-es ˈberodd ní-s ˈess-berodd --- --- --- ---
Lenition es-eh ˈberod Ní-h ˈes-berod kon-eh ˈus-anáθ Ní-h ˈkow̃-us-anáθ dí-h ˈRo-us-skoxíθ Ní-h ˈdi-ro-us-skoxíθ
Palatalization es-eh ˈbʲerod Nʲí-h ˈes-bʲerod --- Nʲí-h ˈkow̃-us-anáθ dʲí-h ˈRo-us-skoxʲíθ Nʲí-h ˈdʲi-ro-us-skoxʲíθ
Hiatus reduction --- --- --- --- dʲí-h ˈRós-skoxʲíθ Nʲí-h ˈdʲi-rós-skoxʲíθ
Umlaut (vowel affection) --- --- kon-eh ˈos-anáθ Nʲí-h ˈkuw̃-us-anáθ --- Nʲí-h ˈdʲe-rós-skoxʲíθ
Shortening of absolutely final vowel --- --- --- --- --- ---
Loss/assimilation of final consonant(s) es-e bʲ-ˈbʲerod Nʲí h-ˈes-bʲerod kon-e h-ˈos-aná Nʲí k-ˈkuw̃-us-aná dʲí R-ˈRós-skoxʲí Nʲí d-ˈdʲe-rós-skoxʲí
Mora reduction in unstressed final vowel es bʲ-ˈbʲerod --- kon h-ˈos-ana Nʲí k-ˈkuw̃-us-ana dʲí R-ˈRós-skoxʲi Nʲí d-ˈdʲe-rós-skoxʲi
Consonant assimilation es ˈbʲerod Nʲí h-ˈebʲ-bʲerod kon h-ˈos-ana Nʲí k-ˈkuw̃-us-ana dʲí R-ˈRós-skoxʲi Nʲí d-ˈdʲe-rós-skoxʲi
Syncope es ˈbʲerod Nʲí h-ˈebʲbʲrod kon h-ˈosna Nʲí k-ˈkuw̃sana dʲí R-ˈRósskxʲi Nʲíd-ˈdʲersskoxʲi
Further consonant assimilation --- Nʲí h-ˈebʲbʲrʲod kon ˈosna --- dʲí R-ˈRósski Nʲíd-ˈdʲerskoxʲi
Unstressed vowel reduction es ˈbʲerǝd Nʲí h-ˈebʲbʲrʲǝd --- Nʲí k-ˈkuw̃sǝna di R-ˈRósski Nʲí d-ˈdʲerskǝxʲi
Prepositional modification as ˈbʲerǝd --- --- --- do R-ˈRósski ---
Geminate reduction (non-vocalic-adjacent); sandhi geminate reduction as·ˈbʲerǝd Nʲíh-ˈebrʲǝd kon·ˈosna Nʲí-ˈkuw̃sǝna do·ˈRóski Nʲí-ˈdʲerskǝxʲi
Fricative voicing between unstressed syllables --- --- --- --- --- Nʲíd-ˈdʲerskǝɣʲi
Old Irish pronunciation as·ˈbʲerǝd Nʲí-h-ˈebrʲǝd kon·ˈosna Nʲí-ˈkuw̃sǝna do·ˈRóski Nʲí-ˈdʲerskǝɣʲi
Old Irish spelling as·berat ní-epret con·osna ní-(c)cumsana do·rósc(a)i ní-(d)derscaigi

The most extreme allomorphy of all came from the third person singular of the s-subjunctive because an athematic person marker -t was used, added directly onto the verbal stem (formed by adding -s directly onto the root). That led to a complex word-final cluster, which was deleted entirely. In the prototonic form (after two proclitics), the root was unstressed and thus the root vowel was also deleted, leaving only the first consonant:

Examples of extreme allomorphy of 3rd person singular s-subjunctive, conjunct[18]
Present Indicative Present Subjunctive
Positive (Deuterotonic) Negative (Prototonic) Positive (Deuterotonic) Negative (Prototonic)
Primitive Irish Old Irish Primitive Irish Old Irish Primitive Irish Old Irish Primitive Irish Old Irish
"he refuses" *uss ˈbond-et(i) as·boind *nís ˈuss-bond-et(i) ní op(a)ind /obǝnʲdʲ/ *uss 'bod-s-t as·bó *nís ˈuss-bod-s-t ní op /ob/
"he remains over" *di ˈwo-uss-ret-et(i) do·fúarat *nís ˈdi-wo-uss-ret-et(i) ní díurat *di ˈwo-uss-ret-s-t do·fúair *nís ˈdi-wo-uss-ret-s-t ní diúair
"he repeats, amends" *ad ˈess-reg-et(i) ad·eirrig *nís ˈ*ad-ess-reg-et(i) (ní aithrig?? >) ní aithirrig *ad ˈess-reg-s-t ath·e(i)rr *nís ˈad-ess-reg-s-t ní aithir
"he can" *con ˈink-et(i) com·ic *nís ˈcom-ink-et(i) ní cum(a)ic > ní cum(u)ing, ní cumaing *con ˈink-s-t con·í *nís ˈcom-ink-s-t, *nís ˈcom-ink-ā-t ní cum, ní cumai
"it happens" *ad ˈcom-ink-et(i) (ad·cum(a)ic >) ad·cumaing *nís ˈad-com-ink-et(i) (ní ecm(a)ic >) ní ecmaing *ad ˈcom-ink-ā-t ad·cumai *nís ˈad-com-ink-ā-t ní ecm(a)i

Syncope in detail

In more detail, syncope of final and intervocalic syllables involved the following steps (in approximate order):

Proto-Celtic short vowels, vowel affection

All five Proto-Celtic short vowels (*a, *e, *i, *o, *u) survived into Primitive Irish more or less unchanged in stressed syllables.

However, during the runup to Old Irish, several mutations (umlauts) take place. Former vowels are modified in various ways depending on the following vowels (or sometimes surrounding consonants). The mutations are known in Celtic literature as affections or infections such as these, the most important ones:[20]

  1. i-affection: Short *e and *o are raised to i and u when the following syllable contains a high vowel (*i, , *u, *k). It does not happen when the vowels are separated by certain consonant groups.
  2. a-affection: Short *i and *u are lowered to e and o when the following syllable contains a non-high back vowel (*a, , *o, ).
  3. u-affection: Short *a, *e, *i are broken to short diphthongs au, eu, iu when the following syllable contains a *u or that was later lost. It is assumed that at the point the change operated, u-vowels that were later lost were short *u while those that remain were long *k. The change operates after i-affection so original *e may end up as iu.

Nominal examples (reconstructed forms are Primitive Irish unless otherwise indicated):

Verbal paradigm example:

form Pronunciation Meaning Prim Irish Post-PIE Comments
Absolute 1sg biru /bʲiru/ "I carry" *berūs *bʰerō + -s i-affection
Absolute 2sg biri /bʲirʲi/ "you (sg.) carry" *berisis *bʰeresi + -s i-affection (unstressed *-es- > *-is- in Primitive Irish, also found in s-stems)
Absolute 3sg berith /bʲirʲǝθʲ/ "he carries" *beretis *bʰereti + -s Unstressed i = /ǝ/ with surrounding palatalised consonants; see #Orthography
Conjunct 1sg ⋅biur /bʲĭŭr/ "I carry" *beru < *berū *bʰerō i-affection + u-affection
Conjunct 2sg bir /bʲirʲ/ "you (sg.) carry" *beris < *berisi *bʰeresi i-affection (unstressed *-es- > *-is- in Primitive Irish)
Conjunct 3sg beir /bʲerʲ/ "he carries" *beret < *bereti *bʰereti i in ei signals palatalisation of following consonant; see #Orthography

The result of i-affection and a-affection is that it is often impossible to distinguish whether the root vowel was originally *e or *i (sen < *senos and fer < *wiros have identical declensions). However, note the cases of nert vs. fiurt above for which i-affection, but not a-affection, was blocked by an intervening rt.

Proto-Celtic long vowels and diphthongs

Proto-Celtic long vowels and diphthongs develop in stressed syllables as follows:

Proto-Celtic archaic Old Irish later Old Irish Example(s)
í (gen. ríg) "king" (cf. Latin rēx, Sanskrit rājan-)
rím "number" (cf. Old High German rīm, Latin rītus "rite")
á máthir "mother" (cf. Latin māter)
dán "gift" (cf. Latin dōnum)
ú cúl "back" (cf. Latin cūlus "ass, buttocks")
*ai /ai/ (spelled áe or ) merged (both spellings used) cáech "one-eyed" < PIE *káikos (cf. Latin caecus "blind", Gothic háihs "one-eyed")
*oi /oi/ (spelled óe or ) oín, óen "one" < PIE *oinos (cf. archaic Latin oenos)
*ei > ē é ía ⋅tíagat "they go" < archaic ⋅tégot < PIE *steigʰ- (cf. Ancient Greek steíkhein "to walk", Gothic steigan ‘to go up’)[21]
*au (+C)[* 2] > ō ó úa úaithed, úathad "singleness" < IE *h₂eu "again" + *to- "that" (cf. Ancient Greek autós "self")
*eu/ou (+C)[* 2] > ō núa, núë "new" < archaic núae < PC *noujos (cf. Gaulish novios) < IE *neu-io-s (cf. Gothic niujis)
túath "tribe, people" < PC *toutā < IE *teutā (cf. Gothic þiuda)
rúad "red" < PC *roudos < PIE *h₁reudʰ- (cf. Gothic rauþs)
*au (not +C)[* 3] áu ó ó < archaic áu, aue "ear" < PC *ausos < IE *h₂eus- (cf. Latin auris)
< archaic náu "ship" < PC *nāwā < PIE *neh₂u- (cf. Latin nāvis)
*ou (not +C)[* 3] óu > áu ‘cow’ < archaic báu < early archaic bóu (c. a.d. 700) < PC *bowos (gen.sg.) < PIE *gʷh₃-eu-

The Old Irish diphthongs úi, éu, íu stem from earlier sequences of short vowels separated by *w, e.g. drúid- "druid" < *dru-wid- "tree-knower".

Most instances of é and ó in nonarchaic Old Irish are due to compensatory lengthening of short vowels before lost consonants or to the merging of two short vowels in hiatus: cét /kʲeːd/ ‘hundred’ < Proto-Celtic kantom (cf. Welsh cant) < PIE *kṃtóm.

PIE consonants


See Proto-Celtic for various changes that occurred in all the Celtic languages, but these are the most important:

From Proto-Celtic to Old Irish, the most important changes are these:

Initial clusters

Old Irish preserves, intact, most initial clusters unlike many other Indo-European languages.

Preserved initial clusters:[23]

Modified initial clusters:[24]

Intervocalic clusters

Many intervocalic clusters are reduced, becoming either a geminate consonant or a simple consonant with compensatory lengthening of the previous vowel. During the Old Irish period, geminates are reduced to simple consonants, occurring earliest when adjacent to a consonant. By the end of the Old Irish period, written ll mm nn rr are repurposed to indicate the non-lenited sounds /L m N R/ when occurring after a vowel and not before a consonant.

Cluster reduction involving *n:

Cluster reduction involving *s *z:

Lenited stops *x generally disappear before sonorants *r *l *n *m, with compensatory lengthening of the preceding vowel. Many examples occur in reduplicated preterites or words with consonant-final prefixes (such as ad-):[6]

However, *θr, *βr, *βl survive: críathraid "he perforates" < PCelt *krētrāti-s; gabur "goat" < PCelt *gabros (cf. Welsh gafr); mebul "shame" (cf. Welsh mefl).


Main article: Old Irish grammar

See also


  1. 1 2 3 4
    • ingen /inʲɣʲǝn/ "daughter" < Ogam inigena < Proto-Celtic *eni-genā (cf. Latin indigenā "(female) native", Ancient Greek engónē "granddaughter".
    • ingen /iNʲɡʲǝn/ "claw, nail" < Proto-Celtic *angʷīnā < PIE *h₃ṇgʷh- (cf. Latin unguis).
  2. 1 2 When followed by a consonant in Old Irish.
  3. 1 2 When not followed by a consonant in Old Irish. This includes words originally followed by *s, which was lost by Old Irish times.
  4. Originally a neuter proterokinetic noun of the form *gʷenh₂ (nom. sg.), *gʷneh₂s (gen. sg.). The original PIE nominative is still preserved in poetic or legal Old Irish N "woman" (still neuter!) < Proto-Celtic *ben < PIE *gʷenh₂. The normal Old Irish nominative is benL (feminine) < Proto-Celtic *benā < *ben + normal feminine *-ā. No other IE language preserves the original neuter gender.


  1. Hammarström, Harald; Forkel, Robert; Haspelmath, Martin; Bank, Sebastian, eds. (2016). "Old Irish (to 900)". Glottolog 2.7. Jena: Max Planck Institute for the Science of Human History.
  2. 1 2 Koch, John Thomas (2006). Celtic culture: a historical encyclopedia. ABC-CLIO. p. 831. The Old Irish of the period c. 600–c. 900 AD is as yet virtually devoid of dialect differences, and may be treated as the common ancestor of the Irish, Scottish Gaelic, and Manx of the Middle Ages and modern period; Old Irish is thus sometimes called 'Old Gaelic' to avoid confusion.
  3. Ó Baoill, Colm (1997). "13: The Scots-Gaelic Interface". The Edinburgh History of the Scots Language. Edinburgh University Press. p. 551. The oldest form of the standard that we have is the language of the period c. AD 600–900, usually called 'Old Irish' – but this use of the word 'Irish' is a misapplication (popular among English-speakers in both Ireland and Scotland), for that period of the language would be more accurately called 'Old Gaelic'.
  4. Thurneysen 1946, p. 4.
  5. Kortlandt 2007, p. 8.
  6. 1 2 Thurneysen 1946, p. 79.
  7. Thurneysen 1946, p. 32.
  8. Kortlandt 2007.
  9. Greene 1973.
  10. Thurneysen 1946, p. 18.
  11. Thurneysen 1946, p. 137.
  12. Thurneysen 1946, p. 181.
  13. Thurneysen 1946, p. 58.
  14. Thurneysen 1946, p. 98.
  15. Thurneysen 1946, pp. 192–193.
  16. Thurneysen 1946, p. 42.
  17. Thurneysen 1946, p. 68.
  18. Fortson 2004, p. 324.
  19. Thurneysen 1946, pp. 70,100.
  20. Thurneysen 1946, pp. 46–50,57.
  21. Thurneysen 1946, p. 36.
  22. Thurneysen 1946, p. 125.
  23. Thurneysen 1946, pp. 128–140.
  24. Thurneysen 1946, pp. 123–139.
  25. Thurneysen 1946, pp. 126–127.


External links

For a list of words relating to Old Irish, see the Old Irish language category of words in Wiktionary, the free dictionary.
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