international auxiliary language

An international auxiliary language (or auxlang) is a language used to enable communication between speakers from different parts of the world who don’t speak each other’s native languages. In the modern era, the de facto IAL is clearly English. There’d also be parts of the world where something else is used as a regional auxiliary language, like Russian in the countries that were formerly part of, or heavily influenced by, the Soviet Union, or French in much of West & North Africa. But overall, globally, English is dominant.

However, English wasn’t designed to serve this role as a language to facilitate communication between non-native speakers. English evolved naturally as the native language of English speakers, and it’s full of irregularities, idioms that have to be memorised, etc.. Its phonology presents some challenges (like the high number of vowels, which also aren’t consistent between accents) and its orthography is notoriously opaque. If you were to design a language to serve as a common bridge between speakers of different languages, instead of just going, “Everyone’s got to speak the language of the most powerful country,” it wouldn’t look like English.

Since the late 19th century, a number of different constructed languages have been devised with the goal of being a better IAL than any natural language. These are generally simpler, with no (or very few) irregularities, and an “international” vocabulary (although what exactly that means is contentious, of course). The idea is that it’s fairer for everyone to learn a simple, neutral second language rather than a difficult natural one closely associated with a specific global power. I consider this a facet of internationalism. The best-known constructed IAL is Esperanto, with about a million people able to speak it to some extent in the modern day. However, it was neither the first, nor is it in my opinion the best – I personally favour Ido, although I think some other IALs have neat ideas too.

The major problem with IALs can, I think, be summed up with xkcd #927(external link). I say this even though I think it’d be a great idea for the world to have one 😛 It’s super easy for people to nitpick at aspects of different projects they don’t like, and then go off to create their own personal IAL, resulting in a profusion of projects with less than a handful of speakers each. That said, since not even the most widespread IAL (Esperanto) has a meaningful fraction of the global reach of English, these are all basically hobby projects anyway and people can do what they find most enjoyable. But for my part, this is why I’d prefer to learn an existing IAL (Ido), rather than, say, developing my own personal dialect of Esperanto “fixing” the things I don’t like about it. I also think it’s better for IAL enthusiasts to be positive about each other’s projects rather than sniping at them all the time. We should also acknowledge that different “families” of IALs (e.g. the Esperantidos, the Romance interlangs…) often share a high degree of mutual intelligibility with each other, so to a large extent it doesn’t matter if you like Ido and your buddy prefers Esperanto; with a modicum of extra effort you can understand each other with both of you speaking your preferred language. That’s a good thing! In the current climate, it’s not likely that any constructed IAL will actually become a major world language any time soon, but if it’s ever going to happen it’ll be more likely if enthusiasts support each other rather than acting like “crabs in a bucket”.

Anyway. The rest of this page is going to talk about different groups of IALs 🙂


Invented in the late 1870s, Volapük gets its own subheading because there’s really nothing to group it with. It was the first IAL to achieve widespread success, claiming over a million speakers at one point. Its grammar was broadly German, while its vocabulary was largely drawn from English, but with the words highly distorted, so as to make them unrecognisable. It was eclipsed within a couple of decades by Esperanto, which was much more regular and easier for people to learn. There are still an estimated 20 enthusiasts using Volapük today, though.

Esperanto & the Esperantidos

Esperanto is a highly regular, agglutinative language first designed by L.L. Zamenhof in 1887. It’s by far the most popular IAL today, with approximately a million people able to speak it to some degree. The internet age has really helped it to thrive, and there are countless blogs, YouTube channels, social media accounts etc. all using the language.

However, in my opinion Esperanto has a number of flaws that limit its attractiveness (to me, personally) as an IAL. Some of these include: its bad approach to gender, with nouns for people being presumed masculine unless you add an affix to make them feminine; its overuse of the prefix mal- to derive some really, really common words; some other words that are derived in a highly idiosyncratic and non-guessable way; the lack of distinction between singular and plural “you”; and some difficult consonant clusters.

Historically, Esperantists have been quite firmly opposed to reform proposals for their language. In part this seems to stem from an idea that if slightly modified versions of Esperanto are allowed, then the modifications will never stop and the whole situation will disintegrate into chaos with different groups of people who think of themselves as “Esperantists” unable to understand each other, which would be a poor outcome for something designed to be an IAL. In modern times, many Esperantists are becoming more open-minded about this, with gender-neutral Esperanto on the rise for example, but there still have been a lot of projects over time to create “fixed” or “improved” Esperantos. These are called Esperantidos (from esperantido, “offspring of Esperanto”).

The first of these (well, first of these to still be spoken today) is Ido, created in 1907 by a largely-French cohort of Esperantists (particularly Louis de Beaufront). I want to admit my bias upfront and say that I really like Ido; it’s my favourite of the proposed IALs and it fixes pretty much everything that pisses me off in Esperanto, while still being very similar (mutual intelligibility is probably like that between Spanish and Italian, I’d say; many function words are different as well as some other vocabulary, but they’re intercomprehensible after a little exposure). Historically Esperantists hated Ido, seeing it as a “betrayal”, but in modern times the majority of them seem to have chilled out. These days, Ido seems to vie with Interlingua for the title of second-most spoken IAL, with approx. one thousand speakers.

Following that, there was the “reformed Ido” that is Novial. Its creator, Otto Jespersen, had been part of the group that invented Ido, but later came to feel that a more naturalistic and irregular language would be better, so invented Novial in 1928. He was highly influenced by Occidental (see below), and in the years prior to his death revamped Novial a few times, bringing it successively closer to Occidental. It drops the regular word class suffixes (like -o for nouns, -a for adjectives, etc.) from Esperanto and Ido, exhibits considerably more verbal complexity by means of auxiliary verbs, and has optional accusative and genitive markers. Novial went mostly dormant after Jespersen’s death in 1943, but there’ve been a few modern revival movements, as well as a few “Novialides”. None of these have gained much traction.

Proyo is a new-ish project which I’ve seen described as a Novialide, although it makes some dramatic departures. It places a high priority on making words easy to pronounce, and makes some other choices I find interesting (e.g. using different endings for intransitive, transitive-with-agent-as-subject and transitive-with-agent-as-object verbs). It uses modal verbs for verb tense and aspect, and makes some useful pronoun distinctions (e.g. between inclusive and exclusive “we”, singular and plural “you”, and it also has a gender-neutral 3rd person pronoun). Just at the minute the creator is too busy with a new job to work much on it, but it looks interesting.

Going back to languages that are closer to the original Esperanto, there is Mondezo, first created in 2001. This Esperantido takes some inspiration from languages that don’t have concepts like noun definiteness or verb tense; in the case of the former you can use “this” or “that” where more specificity is required, and for the latter you can use adverbs to specify when things happen. Word order becomes fixed as SVO (with OSV allowed in relative clauses), adjective-noun agreement is lost, digraphs are used instead of accents, nouns for people are gender-neutral by default with a suffix -ich- being added to denote masculineness.

Romance-ish Naturalistic Languages

There’ve also been a number of proposals for IALs which draw heavily on the Romance languages (sometimes with the addition of English, sometimes without). They tend to be less schematic and more naturalistic than Esperanto or Ido, though still more simplified than the natural Romance languages.

The first Romance naturalistic IAL was Latino sine flexione (also known as “Peano’s Interlingua” or “the first Interlingua”) in 1903. The contention of its creator was that the world didn’t really need a new IAL, because we already had Latin. All that needed to be done was simplify the grammar a bit to make it easier to learn for people who don’t speak such highly-inflected languages as Latin is; Latino sine flexione was the result.

Next there was Occidental, also known as Interlingue, in 1922. I find this the most interesting of the naturalistic IALs because of its effort to codify the really-existing derivation rules of the natural Romance languages. So, basically, it’s like a regularised Romance language, albeit with some Germanic influence too (like in vocabulary, subject pronouns being undroppable, and a very English-like verbal system that uses auxiliary verbs for everything except the simple past tense). The language was basically dormant through the second half of the twentieth century, but has seen a 21st century revival, with perhaps a hundred speakers now.

In 1951 the IALA published Interlingua, which has approximately a thousand speakers in the modern era, but was once well-used enough that some scientific papers were published in it. Compared to Occidental it is much more irregular, and places a lot more emphasis on only using words (including derived words) that actually exist in Interlingua’s source languages (mostly the western Romance languages and English). Personally I think its irregularity makes it a pretty poor candidate for an IAL to anyone except Romance speakers. It might actually have been a good Romance interlang though, except that the desire not to have grammatical features that don’t exist in English (like a non-vestigial subjunctive, or verb conjugation for grammatical person) means it lacks those features which are basically universal across the Romance branch.

Lingua Franca Nova (often known as LFN or Elefen) was published in 1998, having first been created in 1965. It features a highly simplified grammar, influenced by Romance-based creole languages. It’s one of the Romance-likes that does not draw on English as a source language, too. LFN has attracted an active if small community around it, and it has a rockin’ flag.

There are a few other Romance-likes that I don’t know very much about, so I won’t give them full paragraphs, but in some cases I can link to their websites. These include Romániço(external link) (1991), Interlingua Romanica (2001), and Neolatino(external link) (2006). I think these are more strictly Romance interlangs, not overtly influenced by English. Neolatino in particular seems to have a fair amount of reading material for it.

Other Indo-European

Sambahsa is an IAL based largely on Proto-Indo-European, with some other borrowings (e.g. from Arabic, Chinese, Indonesian, Turkish and Swahili). The phonology is not especially close to PIE, but it does have a lot of inflectional complexity. It also tends to use more conservative, etymological spellings, which makes the orthography complex.

Interslavic deserves an honourable mention even though it’s not strictly an IAL. As the name suggests, it is a Slavic interlanguage, and with a few thousand speakers it’s actually the second most spoken constructed language in the world, behind Esperanto.

Mešanka is a newer interlanguage, which aims to be to Interslavic what Occidental is to Interlingua: that is, much more regular while still looking naturalistic.

Some other Indo-European proposals, which may or may not have any actual speakers, include Ekumenski (current) and Uropi (1990s).


A worldlang is a language that attempts to be as globally-representative as possible, rather than mainly just representing the vocabularies and grammars of European languages (or any other subset of the world’s languages).

Pandunia was first invented in 2007, but has seemingly never reached the point of releasing a stable version that could be added to incrementally over time. Instead, the language goes through massive root-and-branch overhauls every few years. For example, it has oscillated between being isolating (v0.x and v2) and agglutinative (v1), and revamped its phonemic inventory and personal pronoun paradigm repeatedly. It draws on 13 source languages (English, Chinese, French, Spanish, Arabic, Russian, Hindi-Urdu, Japanese, Portuguese, Malay, Korean, Bengali and Swahili).

Globasa is a newer project to develop a globally-representative language, with nine source families (Romance, Germanic, Slavic, Semitic, Turkic, Iranian, Indic, Dravidian, Malayo-Polynesian) and five further source languages (Chinese, Japanese, Korean, Vietnamese, Swahili) to adopt vocabulary from. Its grammar is analytic and isolating, with things like verb tense and noun number and definiteness marked with optional ad­verbs/ad­jec­tives. It was first published in 2019, and has been fairly stable ever since, with the major changes being additional vocabulary.

Lingwa de Planeta(external link), first published in 2010, is another worldlang. It seems to be inspired in part by Novial, and makes greater use of affixes to derive words than the languages listed above. Its technical vocabulary is largely drawn from Novial (and therefore from that Greco-Roman reserve of words that tends to supply the technical vocab for not only European languages but many others). However, the most frequent words are sourced from English, Russian, Chinese, Arabic and Hindi. Verb tense, aspect and mood are expressed mostly by means of added particles (with the exception that the past tense is expressed with the suffix -te). In general the grammar is more complicated, and less “creole-like”, than other worldlangs.

One other proposal I know of is Lugamun(external link), but I know very little about it.

A Priori

An a priori language is a language that makes all its vocabulary up, rather than borrowing words from any natural language. The only one I’ve really even somewhat heard of is Kotava, invented in 1978. Apparently it has about 40–50 speakers, mostly in French-speaking countries, and is difficult to learn if you don’t speak French because that’s what all the self-teaching resources are in. Its speakers are pretty active, having translated a bunch of literature into the language and written more articles for the Kotava edition of Wikipedia than exist even in the Interlingua one.