Proto-Bantu (also Common Bantu) is the reconstructed common ancestor of most Bantu languages. It is thought to have originally been spoken in West/Central Africa in the area of what is now Cameroon. Approximately 3000–4000 years ago, it split off from other Niger–Congo languages when the Bantu expansion began to the south and east.
- The voiceless consonants *p, *t, *k were almost certainly articulated as simple plosives [p], [t], [k].
- The voiced consonants *b and *g may also have been fricatives [β] (or [v]) and [ɣ] in some environments.
- *d was a plosive [d] before a high vowel (*i, *u), and a lateral [l] before other vowels.
- *c and *j may have been plosives [ɣ] and [ɟ], affricates [tʃ] and [dʒ], or even sibilants [s] and [z]. [j] is also possible for *j.
Consonants could not occur at the end of a syllable, only at the beginning, so the syllable structure was generally V or CV and all syllables were open. Consonant clusters did not occur, except for the "pre-nasalised" consonants.
The so-called "pre-nasalised" consonants were sequences of a nasal and a following obstruent. These could occur anywhere a single consonant was permitted, including word-initially. Pre-nasalised voiceless consonants were rare, most were voiced. The nasal's articulation adapted to the articulation of the following consonant, so the nasal can be considered a single unspecified nasal phoneme (indicated as *N) which had four possible allophones. Conventionally, the labial pre-nasal is written *m while the others are written *n.
- *mb, *mp; phonemically *Nb, *Np
- *nd, *nt; phonemically *Nd, *Nt
- *nj, *nc; phonemically *Nj, *Nc (actually pronounced as *ɲj, *ɲc)
- *ng, *nk; phonemically *Ng, *Nk (actually pronounced as *ŋg, *ŋk)
The earlier velar nasal phoneme /ŋ/, which was present in the Bantoid languages, had been lost in Proto-Bantu. It still occurred phonetically in pre-nasalised consonants, but not as a phoneme.
The representation of the vowels may differ in particular with respect to the two "middle" levels of closedness. Most linguists write the "less closed" set as *ɪ and *ʊ. However, some prefer to denote them as *e and *o, with the more open set represented as *ɛ and *ɔ. Regardless of the representation, the third level (*e and *o in the table) was open-mid [ɛ] and [ɔ].
Syllables always ended in a vowel, but could also begin with one. Vowels could also occasionally appear in a sequence, but did not form diphthongs; two adjacent vowels were separate syllables. If two of the same vowel occurred together, this created a long vowel, although this was rare.
Proto-Bantu distinguished two tones, low and high. Each syllable had either a low or a high tone. A high tone is conventionally indicated with an acute accent (´) while a low tone is either indicated with a grave accent (`) or not marked at all.
Proto-Bantu, like its descendants, had an elaborate system of noun classes. Noun stems were prefixed with a noun prefix which specified its meaning. Other words that related or referred to that noun, such as adjectives and verbs, also received a prefix that matched the class of the noun ("agreement" or "concord").
The following table gives a reconstruction of the system of nominal classes. The spellings have been normalised to use the ɪ and ʊ notations.
|2||*ba-||*va-||*va-||*ba-||Plural of class 1|
|4||*mɪ-||*mɪ-||*mɪ-||*mɪ-||Plural of class 3|
|6||*ma-||*ma-||*ma-||*ma-||Plural of class 5, liquids (mass nouns)|
|7||*kɪ-||*kɪ-||*kɪ-||*kɪ-||Various, diminutives, manner/way/language|
|8||*bi-||*ʋi-, *li- ("8x")||*ʋi-, *di-||*bi-||Plural of class 7|
|10||*n-||*li-nɪ-||*di-n-||*n-||Plural of class 9 and 11|
|13||*tʊ-||*tʊ-||*tʊ-||*tʊ-||Plural of class 12|
|16||*pa-||*pa-||*pa-||*pa-||Locatives (proximal, exact)|
|17||*kʊ-||*kʊ-||*kʊ-||*kʊ-||Locatives (distal, approximate)|