A planned or constructed language (sometimes called a conlang) is a language whose phonology, grammar, and vocabulary have been consciously devised for human or human-like communication, instead of having developed naturally. It is also referred to as an artificial or invented language. There are many possible reasons to create a constructed language, such as: to ease human communication (see international auxiliary language and code), to give fiction or an associated constructed setting an added layer of realism, for experimentation in the fields of linguistics, cognitive science, and machine learning, for artistic creation, and for language games.
The expression planned language is sometimes used to mean international auxiliary languages and other languages designed for actual use in human communication. Some prefer it to the adjective artificial, for the latter may be perceived as pejorative. Outside Esperanto culture, the term language planning means the prescriptions given to a natural language to standardize it; in this regard, even "natural languages" may be artificial in some respects. Prescriptive grammars, which date to ancient times for classical languages such as Latin and Sanskrit, are rule-based codifications of natural languages, such codifications being a middle ground between naive natural selection and development of language and its explicit construction. The term glossopoeia is also used to mean language construction, particularly construction of artistic languages.
As a quantitative example of the use of conlangs within a country, the Hungarian census of 2001 found 4570 speakers of Esperanto, 10 of Romanid, 2 each of Interlingua and Ido and 1 each of Idiom Neutral and Mundolinco. The Russian census of 2010 found 992 speakers of Esperanto, 9 of Ido, 1 of Edo and no speakers of Slovio or Interlingua.
Planned, constructed, artificial
The terms "planned", "constructed", and "artificial" are used differently in some traditions. For example, few speakers of Interlingua consider their language artificial, since they assert that it has no invented content: Interlingua's vocabulary is taken from a small set of natural languages, and its grammar is based closely on these source languages, even including some degree of irregularity; its proponents prefer to describe its vocabulary and grammar as standardized rather than artificial or constructed. Similarly, Latino sine flexione (LsF) is a simplification of Latin from which the inflections have been removed. As with Interlingua, some prefer to describe its development as "planning" rather than "constructing". Some speakers of Esperanto and Esperantidos also avoid the term "artificial language" because they deny that there is anything "unnatural" about the use of their language in human communication.
By contrast, some philosophers have argued that all human languages are conventional or artificial. François Rabelais, for instance, stated: "C'est abus de dire que nous avons une langue naturelle; les langues sont par institution arbitraires et conventions des peuples." (It's an abuse to say that we have a natural language; languages are arbitrary and conventions of peoples by institution.)
An artificial language can also refer to a language that emerges naturally out of experimental studies within the framework of artificial language evolution.
Further, fictional and experimental languages can be naturalistic in that they are meant to sound natural, have realistic amounts of irregularity, and, if derived a posteriori from a real-world natural language or a real-world reconstructed proto-language (such as Vulgar Latin or Proto-Indo-European) or from a fictional proto-language, they try to imitate natural processes of phonological, lexical, and grammatical change. In contrast with Interlingua, they are not usually intended for easy learning or communication, and most artlangers do not consider Interlingua to be naturalistic in the sense in which this term is used in artlang criticism. Thus, a naturalistic fictional language tends to be more difficult and complex. While Interlingua has simpler grammar, syntax, and orthography than its source languages (though more complex and irregular than Esperanto or its descendants), naturalistic fictional languages typically mimic behaviors of natural languages like irregular verbs and nouns and complicated phonological processes.
In terms of purpose, most constructed languages can broadly be divided into:
- Engineered languages (engelangs /ˈɛnd͡ʒlæŋz/), further subdivided into logical languages (loglangs), philosophical languages and experimental languages; devised for the purpose of experimentation in logic, philosophy, or linguistics;
- Auxiliary languages (auxlangs) devised for international communication (also IALs, for International Auxiliary Language);
- Artistic languages (artlangs) devised to create aesthetic pleasure or humorous effect, just for fun; usually secret languages and mystical languages are classified as artlangs.
The boundaries between these categories are by no means clear. A constructed language could easily fall into more than one of the above categories. A logical language created for aesthetic reasons would also be classifiable as an artistic language, which might be created by someone with philosophical motives intending for said conlang to be used as an auxiliary language. There are no rules, either inherent in the process of language construction or externally imposed, that would limit a constructed language to fitting only one of the above categories.
A constructed language can have native speakers if young children learn it from parents who speak it fluently. According to Ethnologue, there are "200–2000 who speak Esperanto as a first language". A member of the Klingon Language Institute, d'Armond Speers, attempted to raise his son as a native (bilingual with English) Klingon speaker.
As soon as a constructed language has a community of fluent speakers, especially if it has numerous native speakers, it begins to evolve and hence loses its constructed status. For example, Modern Hebrew and its pronunciation norms were developed from existing traditions of Hebrew, such as Mishnaic Hebrew and Biblical Hebrew following a general Sephardic pronunciation, rather than engineered from scratch, and has undergone considerable changes since the state of Israel was founded in 1948 (Hetzron 1990:693). However, linguist Ghil'ad Zuckermann argues that Modern Hebrew, which he terms "Israeli", is a Semito-European hybrid based not only on Hebrew but also on Yiddish and other languages spoken by revivalists. Zuckermann therefore endorses the translation of the Hebrew Bible into what he calls "Israeli". Esperanto as a living spoken language has evolved significantly from the prescriptive blueprint published in 1887, so that modern editions of the Fundamenta Krestomatio, a 1903 collection of early texts in the language, require many footnotes on the syntactic and lexical differences between early and modern Esperanto.
Proponents of constructed languages often have many reasons for using them. The famous but disputed Sapir–Whorf hypothesis is sometimes cited; this claims that the language one speaks influences the way one thinks. Thus, a "better" language should allow the speaker to think more clearly or intelligently or to encompass more points of view; this was the intention of Suzette Haden Elgin in creating Láadan, a feminist language embodied in her feminist science fiction series Native Tongue. A constructed language could also be used to restrict thought, as in George Orwell's Newspeak, or to simplify thought, as in Toki Pona. In contrast, linguists such as Steven Pinker argue that ideas exist independently of language. For example, in the book The Language Instinct, Pinker states that children spontaneously re-invent slang and even grammar with each generation. These linguists argue that attempts to control the range of human thought through the reform of language would fail, as concepts like "freedom" will reappear in new words if the old words vanish.
Proponents claim a particular language makes it easier to express and understand concepts in one area, and more difficult in others. An example can be taken from the way various programming languages make it easier to write certain kinds of programs and harder to write others.
Another reason cited for using a constructed language is the telescope rule, which claims that it takes less time to first learn a simple constructed language and then a natural language, than to learn only a natural language. Thus, if someone wants to learn English, some suggest learning Basic English first. Constructed languages like Esperanto and Intelingua are in fact often simpler due to the typical lack of irregular verbs and other grammatical quirks. Some studies have found that learning Esperanto helps in learning a non-constructed language later (see propaedeutic value of Esperanto).
Codes for constructed languages include the ISO 639-2 "art" for conlangs; however, some constructed languages have their own ISO 639 language codes (e.g. "eo" and "epo" for Esperanto, "jbo" for Lojban, "ia" and "ina" for Interlingua, "tlh" for Klingon and "io" and "ido" for Ido).
A priori and a posteriori languages
An a priori constructed language is one whose features (including vocabulary, grammar, etc.) are not based on an existing language, and an a posteriori language is the opposite. This categorization, however, is not absolute, as many constructed languages may be both a priori and a posteriori depending on which linguistic factors of them are observed.
a priori language
An a priori language (from Latin a priori, "from the former") is any constructed language of which all or a number of features are not based on existing languages, but rather invented or elaborated as to work in a different way or to allude different purposes. Some a priori languages are designed to be international auxiliary languages that remove what could be considered an unfair learning advantage for native speakers of a source language that would otherwise exist for a posteriori languages. Other, known as philosophical or taxonomic languages, try to categorize their vocabulary, either to express an underlying philosophy or to make it easier to recognize new vocabulary.
There have been many languages constructed to test linguistic hypotheses (such as the Sapir–Whorf hypothesis) and/or to explore innovative or invented linguistic features. They are therefore necessarily designed with a priori features. Examples include Ithkuil, Kotava, Lojban (and its predecessor Loglan, both of which are also schematic), and even the fictional-setting Láadan.
Most artistic languages, i.e. those created for amusement or to serve as natural languages of fictional worlds, are largely a priori in both vocabulary and grammar. Among classical "fictional natural languages" are Klingon from the science-fiction franchise Star Trek and the languages created by fantasy writer J. R. R. Tolkien. Other examples include Dothraki and Valyrian from Game of Thrones, Atlantean from Atlantis: The Lost Empire, Kēlen by Sylvia Sotomayor and aUI by W. John Weilgart. Láadan is both experimental and artistic.
a posteriori language
An a posteriori language (from Latin a posteriori, "from the later"), according to Louis Couturat, is any constructed language whose elements are borrowed from or based on existing languages. The term can also be extended to controlled versions of existing languages, and is most commonly used to refer to vocabulary despite other features. In distinguishing whether the language is a priori or a posteriori, the prevalence and distribution of respectable traits is often the key. They may be controlled, naturalistic or schematic.
Naturalistic languages are constructed languages which largely imitate the grammar and vocabulary of a particular group of related languages within a family, thus being potentially zonal, i.e. auxiliary between speakers of these languages.
A constructed language is considered schematic when it features a more original grammar, which is usually precise and regular as to avoid ambiguities and other obstacles to an easy study, and a vocabulary coming from languages of different families, to make it as recognizable as possible for potential international auxiliary purposes. For that they can be described as half a priori, half a posteriori. There have been many attempts of developing languages with these characteristics, including:
Ancient linguistic experiments
Grammatical speculation dates from Classical Antiquity, appearing for instance in Plato's Cratylus in Hermogenes's contention that words are not inherently linked to what they refer to; that people apply "a piece of their own voice ... to the thing". Athenaeus of Naucratis, in Book III of Deipnosophistae, tells the story of two figures: Dionysius of Sicily and Alexarchus. Dionysius of Sicily created neologisms like menandros "virgin" (from menei "waiting" and andra "husband"), menekratēs "pillar" (from menei "it remains in one place" and kratei "it is strong"), and ballantion "javelin" (from balletai enantion "thrown against someone"). Incidentally, the more common Greek words for those three are parthenos, stulos, and akon. Alexarchus of Macedon, the brother of King Cassander of Macedon, was the founder of the city of Ouranopolis. Athenaeus recounts a story told by Heracleides of Lembos that Alexarchus "introduced a peculiar vocabulary, referring to a rooster as a "dawn-crier," a barber as a "mortal-shaver," a drachma as "worked silver"...and a herald as an aputēs [from ēputa "loud-voiced"]. "He once wrote something...to the public authorities in Casandreia...As for what this letter says, in my opinion not even the Pythian god could make sense of it." While the mechanisms of grammar suggested by classical philosophers were designed to explain existing languages (Latin, Greek, Sanskrit), they were not used to construct new grammars. Roughly contemporary to Plato, in his descriptive grammar of Sanskrit, Pāṇini constructed a set of rules for explaining language, so that the text of his grammar may be considered a mixture of natural and constructed language.
Early constructed languages
A legend recorded in the seventh-century Irish work Auraicept na n-Éces claims that Fénius Farsaid visited Shinar after the confusion of tongues, and he and his scholars studied the various languages for ten years, taking the best features of each to create in Bérla tóbaide ("the selected language"), which he named Goídelc — the Irish language. This appears to be the first mention of the concept of a constructed language in literature.
The earliest non-natural languages were considered less "constructed" than "super-natural", mystical, or divinely inspired. The Lingua Ignota, recorded in the 12th century by St. Hildegard of Bingen is an example, and apparently the first entirely artificial language. It is a form of private mystical cant (see also language of angels). An important example from Middle-Eastern culture is Balaibalan, invented in the 16th century. Kabbalistic grammatical speculation was directed at recovering the original language spoken by Adam and Eve in Paradise, lost in the confusion of tongues. The first Christian project for an ideal language is outlined in Dante Alighieri's De vulgari eloquentia, where he searches for the ideal Italian vernacular suited for literature. Ramon Llull's Ars Magna was a project of a perfect language with which the infidels could be convinced of the truth of the Christian faith. It was basically an application of combinatorics on a given set of concepts. During the Renaissance, Lullian and Kabbalistic ideas were drawn upon in a magical context, resulting in cryptographic applications. The Voynich manuscript may be an example of this.
Renaissance interest in Ancient Egypt, notably the discovery of the Hieroglyphica of Horapollo, and first encounters with the Chinese script directed efforts towards a perfect written language. Johannes Trithemius, in Steganographia and Polygraphia, attempted to show how all languages can be reduced to one. In the 17th century, interest in magical languages was continued by the Rosicrucians and Alchemists (like John Dee and his Enochian). Jakob Boehme in 1623 spoke of a "natural language" (Natursprache) of the senses.
Musical languages from the Renaissance were tied up with mysticism, magic and alchemy, sometimes also referred to as the language of the birds. The Solresol project of 1817 re-invented the concept in a more pragmatic context.
17th and 18th century: advent of philosophical languages
The 17th century saw the rise of projects for "philosophical" or "a priori" languages, such as:
- Francis Lodwick's A Common Writing (1647) and The Groundwork or Foundation laid (or So Intended) for the Framing of a New Perfect Language and a Universal Common Writing (1652)
- Sir Thomas Urquhart's Ekskybalauron (1651) and Logopandecteision (1652)
- George Dalgarno's Ars signorum, 1661
- John Wilkins' Essay towards a Real Character, and a Philosophical Language, 1668
These early taxonomic conlangs produced systems of hierarchical classification that were intended to result in both spoken and written expression. Leibniz had a similar purpose for his lingua generalis of 1678, aiming at a lexicon of characters upon which the user might perform calculations that would yield true propositions automatically, as a side-effect developing binary calculus. These projects were not only occupied with reducing or modelling grammar, but also with the arrangement of all human knowledge into "characters" or hierarchies, an idea that with the Enlightenment would ultimately lead to the Encyclopédie. Many of these 17th−18th centuries conlangs were pasigraphies, or purely written languages with no spoken form or a spoken form that would vary greatly according to the native language of the reader.
Leibniz and the encyclopedists realized that it is impossible to organize human knowledge unequivocally in a tree diagram, and consequently to construct an a priori language based on such a classification of concepts. Under the entry Charactère, D'Alembert critically reviewed the projects of philosophical languages of the preceding century. After the Encyclopédie, projects for a priori languages moved more and more to the lunatic fringe. Individual authors, typically unaware of the history of the idea, continued to propose taxonomic philosophical languages until the early 20th century (e.g. Ro), but most recent engineered languages have had more modest goals; some are limited to a specific field, like mathematical formalism or calculus (e.g. Lincos and programming languages), others are designed for eliminating syntactical ambiguity (e.g., Loglan and Lojban) or maximizing conciseness (e.g., Ithkuil).
19th and 20th century: auxiliary languages
Already in the Encyclopédie attention began to focus on a posteriori auxiliary languages. Joachim Faiguet de Villeneuve in the article on Langue wrote a short proposition of a "laconic" or regularized grammar of French. During the 19th century, a bewildering variety of such International Auxiliary Languages (IALs) were proposed, so that Louis Couturat and Léopold Leau in Histoire de la langue universelle (1903) reviewed 38 projects.
The first of these that made any international impact was Volapük, proposed in 1879 by Johann Martin Schleyer; within a decade, 283 Volapükist clubs were counted all over the globe. However, disagreements between Schleyer and some prominent users of the language led to schism, and by the mid-1890s it fell into obscurity, making way for Esperanto, proposed in 1887 by Ludwik Lejzer Zamenhof, and its descendants. Interlingua, the most recent auxlang to gain a significant number of speakers, emerged in 1951, when the International Auxiliary Language Association published its Interlingua–English Dictionary and an accompanying grammar. The success of Esperanto did not stop others from trying to construct new auxiliary languages, such as Leslie Jones' Eurolengo, which mixes elements of English and Spanish, or He Yafu's Mondlango, which introduces more English roots instead of Latin ones.
Loglan (1955) and its descendants constitute a pragmatic return to the aims of the a priori languages, tempered by the requirement of usability of an auxiliary language. Thus far, these modern a priori languages have garnered only small groups of speakers.
Robot Interaction Language (2010) is a spoken language that is optimized for communication between machines and humans. The major goals of ROILA are that it should be easily learnable by the human user, and optimized for efficient recognition by computer speech recognition algorithms.
Artistic languages, constructed for literary enjoyment or aesthetic reasons without any claim of usefulness, begin to appear in Early Modern literature (in Pantagruel, and in Utopian contexts), but they only seem to gain notability as serious projects beginning in the 20th century. A Princess of Mars (1912) by Edgar Rice Burroughs was possibly the first fiction of that century to feature a constructed language. J. R. R. Tolkien developed a family of related fictional languages and discussed artistic languages publicly, giving a lecture entitled "A Secret Vice" in 1931 at a congress. (Orwell's Newspeak is considered a satire of an IAL rather than an artistic language proper.)
By the beginning of the first decade of the 21st century, it had become common for science-fiction and fantasy works set in other worlds to feature constructed languages, or more commonly, an extremely limited but defined vocabulary which suggests the existence of a complete language, and constructed languages are a regular part of the genre, appearing in Star Wars, Star Trek, Lord of the Rings (Elvish), Stargate SG-1, Atlantis: The Lost Empire, Game of Thrones (Dothraki language and Valyrian languages), Avatar, Dune and the Myst series of computer adventure games.
Modern conlang organizations
Various paper zines on constructed languages were published from the 1970s through the 1990s, such as Glossopoeic Quarterly, Taboo Jadoo, and The Journal of Planned Languages. The Conlang Mailing List was founded in 1991, and later split off an AUXLANG mailing list dedicated to international auxiliary languages. In the early to mid-1990s a few conlang-related zines were published as email or websites, such as Vortpunoj and Model Languages. The Conlang mailing list has developed a community of conlangers with its own customs, such as translation challenges and translation relays, and its own terminology. Sarah Higley reports from results of her surveys that the demographics of the Conlang list are primarily men from North America and western Europe, with a smaller number from Oceania, Asia, the Middle East, and South America, with an age range from thirteen to over sixty; the number of women participating has increased over time.
More recently founded online communities include the Zompist Bulletin Board (ZBB; since 2001) and the Conlanger Bulletin Board. Discussion on these forums includes presentation of members' conlangs and feedback from other members, discussion of natural languages, whether particular conlang features have natural language precedents, and how interesting features of natural languages can be repurposed for conlangs, posting of interesting short texts as translation challenges, and meta-discussion about the philosophy of conlanging, conlangers' purposes, and whether conlanging is an art or a hobby. Another 2001 survey by Patrick Jarrett showed an average age of 30.65, with the average time since starting to invent languages 11.83 years. A more recent thread on the ZBB showed that many conlangers spend a relatively small amount of time on any one conlang, moving from one project to another; about a third spend years on developing the same language.
Collaborative constructed languages
The Talossan language, a cultural base for the micronation known as Talossa, was created by a single person in 1979. However, as interest in Talossan grew, guidance of the language became (in 1983) the province of a recommending body, the Comità per l'Útzil del Glheþ, and other independent organizations of enthusiasts. Villnian draws on Latin, Greek and the Scandinavian languages. In its syntax and grammar it is reminiscent of Chinese. The core elements were created by a single person, and its vocabulary is now enlarged by suggestions from the internet community.
While most constructed languages begin as did Talossan, having been created by a single person, a few are created by group collaborations; examples of these are Interlingua, which was developed by the International Auxiliary Language Association, and Lojban, which was developed by a breakaway group of Loglanists.
Group collaboration has apparently become more common in recent years, as constructed language designers have started using Internet tools to coordinate design efforts. NGL/Tokcir was an early Internet collaborative engineered language whose designers used a mailing list to discuss and vote on grammatical and lexical design issues. More recently, The Demos IAL Project was developing an international auxiliary language with similar collaborative methods. The Voksigid and Novial 98 languages were both worked on by mailing lists, though neither was issued in final form.
Several artistic languages have been developed on different constructed language wikis, usually involving discussion and voting on phonology, grammatical rules, and so forth. An interesting variation is the corpus approach, exemplified by Madjal and Kalusa (mid-2006), where contributors simply read the corpus of existing sentences and add their own sentences, perhaps reinforcing existing trends or adding new words and structures. The Kalusa engine adds the ability for visitors to rate sentences acceptable or unacceptable. There is no explicit statement of grammatical rules or explicit definition of words in this corpus approach; the meaning of words is inferred from their use in various sentences of the corpus, perhaps in different ways by different readers and contributors, and the grammatical rules can be inferred from the structures of the sentences that have been rated highest by the contributors and other visitors.
- List of constructed languages
- Aboriginal constructed languages: Damin, Eskayan
- ISO, SIL, and BCP language codes for constructed languages
- Language construction
- Language modelling and translation
- Mystical languages
- Spontaneous emergence of grammar
- Linguistic determinism
- Linguistic relativity
- Universal language
- Basic English
- Adrian Morgan. "Conlanging and phonetics". The Outer Hoard. "The colours represent creative energy, and the layers of the tower imply that a conlang is built piece by piece, never completed. The tower itself also alludes to the Tower of Babel, as it has long been a tradition to demonstrate a constructed language by translating the Babel legend. The Conlang flag was decided on by a vote between many competing designs, and one of my own contributions to the conlanging world is that I was the person who facilitated this election. The winning design was drawn by Christian Thalmann, who introduced the layers. The idea of including the Tower of Babel on the flag had been introduced by Jan van Steenbergen, and the idea of placing the sun on the horizon behind it by Leland Paul. The idea of having the rising sun on the flag had been introduced by David Peterson, who saw it as representing the rise of conlanging from obscurity to popularity and notoriety."
- "Ishtar for Belgium to Belgrade". European Broadcasting Union. Retrieved 19 May 2013.
- Sarah L. Higley: Hildegard of Bingen's Unknown Language. Palgrave Macmillan, 2007.
- Ethnic affiliation, attachment of cultures, languages and language systems Hungarian statistical office
- Russian census (2010)
- François Rabelais, Œvres complètes, III, 19 (Paris: Seuil, 1973), cited in Claude Piron, Le Defi des Langues (L'Harmattan, 1994) ISBN 2-7384-2432-5.
- "Re: "Naturalistic" for auxlangers vs artlangers?" AUXLANG mailing list post by Jörg Rhiemeier, 30 August 2009
- The "Conlang Triangle" by Raymond Brown. Accessed 8 August 2008
- Gavin Edwards: Babble On Revisited, Wired Magazine, Issue 7.08, August 1999
- Hybridity versus Revivability: Multiple Causation, Forms and Patterns, Ghil'ad Zuckermann, Journal of Language Contact, Varia 2, pp. 40-67 (2009).
- Let my people know!, Ghil'ad Zuckermann, Jerusalem Post, May 18, 2009.
- Fundamenta Krestomatio, ed. L. L. Zamenhof, 1903; 18th edition with footnotes by Gaston Waringhien, UEA 1992.
- Joshua Foer, "John Quijada and Ithkuil, the Language He Invented", The New Yorker, Dec. 24, 2012.
- "My hypothesis was that if I constructed a language designed specifically to provide a more adequate mechanism for expressing women's perceptions, women would (a) embrace it and begin using it, or (b) embrace the idea but not the language, say "Elgin, you've got it all wrong!" and construct some other "women's language" to replace it." Glatzer, Jenna (2007). "Interview With Suzette Haden Elgin". Archived from the original on 2007-06-12. Retrieved 2007-03-20.
- "Logopandecteision". uchicago.edu.
- Leopold Einstein, "Al la historio de la Provoj de Lingvoj Tutmondaj de Leibnitz ĝis la Nuna Tempo", 1884. Reprinted in Fundamenta Krestomatio, UEA 1992 .
- "How did you find out that there were other conlangers?" Conlang list posting by And Rosta, 14 October 2007
- Archives of Vortpunoj at Steve Brewer's website
- Audience, Uglossia, and Conlang: Inventing Languages on the Internet by Sarah L. Higley. M/C: A Journal of Media and Culture 3.1 (2000). (Archived June 16, 2005, at the Wayback Machine., media-culture.org.au site sometimes has problems.)
- "Update mailing list statistics—FINAL", Conlang list posting by Patrick Jarrett, 13 September 2001
- "Average life of a conlang" thread on Zompist Bulletin Board, 15 August 2008; accessed 26 August 2008.
"Average life of a conlang" thread on Conlang mailing list, 27 August 2008 (should be archived more persistently than the ZBB thread)
- "NGL Central Repository". geocities.com. Archived from the original on 27 October 2009.
- "Yahoo! Groups". yahoo.com.
- Shannon, Gary (2004). "Madjal: A Non‑Constructed Language Born of Linguistic Chaos and Anarchy". Archived from the original on 20 November 2008.
- The 2006 Smiley Award Winner: Kalusa by David J. Peterson
- Eco, Umberto (1995). The search for the perfect language. Oxford: Blackwell. ISBN 0-631-17465-6.
- Comrie, Bernard (1990). The World's Major Languages. Oxford [Oxfordshire]: Oxford University Press. ISBN 0-19-506511-5.
- Couturat, Louis (1907). Les nouvelles langues internationales. Paris: Hachette. With Léopold Leau. Republished 2001, Olms.
- Couturat, Louis (1910). Étude sur la dérivation dans la langue internationales. Paris: Delagrave. 100 p.
- Libert, Alan (2000). A priori artificial languages (Languages of the world). Lincom Europa. ISBN 3-89586-667-9.
- Okrent, Arika (2009). In the Land of Invented Languages: Esperanto Rock Stars, Klingon Poets, Loglan Lovers, and the Mad Dreamers Who Tried to Build A Perfect Language. Spiegel & Grau. p. 352. ISBN 0-385-52788-8.
- "Babel's modern architects", by Amber Dance. The Los Angeles Times, 24 August 2007 (Originally published as "In their own words -- literally")
- Constructed language at DMOZ
- Conlang Atlas of Language Structures, a typological database of conlangs, based on the World Atlas of Language Structures.
- Blueprints For Babel, focusing on international auxiliary languages.
- Garrett's Links to Logical Languages
- Department of Planned Languages Esperanto Museum of the Austrian National Library.
- The Conlanger's Library
- Henrik Theiling's (Con)Language Resources
- Jörg Rhiemeier's Conlang Page