What (if any) are the structural similarities that all languages share that allows them to be taken in and learned by virtually all humans starting at a very young age?

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    This question is laden with presuppositions that aren't necessarily true, viz. that all languages have structural similarities (likely untrue barring trivialities like all languages having vowels and consonants) and that such structural similarities facilitate language acquisition (structural similarities, even if they exist can arise for purposes other than facilitating acquisition). Jun 2, 2018 at 11:51
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    I think you'd be better off asking for some plausible candidates for such structural similarities. Jun 2, 2018 at 11:56
  • When it comes to structures all languages have constituents and express information structure through word order (though not exclusively). Psycholinguistic research indicates information structure is acquired before syntax proper (dependencies).
    – Atamiri
    Jun 9, 2018 at 11:19

2 Answers 2


For any specific property you suggest, there's probably a counter-example somewhere. However, the big one that's most often considered universal is recursion.

Every known human language (*) has recursion: some way of embedding one clause into another one, to an arbitrary depth. In English, you can use relative clauses, like "I saw the man who saw the woman who saw…", or complementizers, like "I told Alice that Bob told Claire that…". And while the exact mechanics differ, every language has some way of doing this.

(*) There's one often-cited counterexample, Pirahã. However, the work claiming that Pirahã lacks recursion is…controversial. Nobody except the original researcher has been able to check the evidence, and Pirahã is claimed to have quite a lot of properties that are unlike any other language on Earth. It seems more reasonable to treat it as a bad data point.

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    From what I understand, the current generativist position is that the “recursion” that is hypothesized to be part of UG does not mean “some way of embedding one clause into another one, to an arbitrary depth”. As best as I can understand it, “recursion” is instead used to refer to the ability to construct phrases from smaller parts using something like “merge”. So e.g., being able to combine an adjective with a noun to make a noun phrase would count as an example of “recursion” in this sense. Jun 1, 2018 at 23:49
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    @sumelic My understanding was that it only counted as recursion if the new phrase had the same type as one of its components. So making a noun phrase out of a noun and an adjective wouldn't count, but making a noun phrase out of a noun phrase and an adjective would. That's what lets it become infinite.
    – Draconis
    Jun 2, 2018 at 1:38
  • Well, I don't understand the details of the argument very well, but see the quotes in my answer to the following question: What is recursion? Jun 2, 2018 at 17:46
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    There seems to be a weird phenomenon where generative grammarians make some claim that they say means something almost trivially true, but that also can be misinterpreted as meaning something more interesting but also less obviously true, and opponents of generativism attempt to disprove the more interesting claim, and then the generativists say "that's irrelevant". I don't know to what extent this is driven by the opponents of generativism misunderstanding things vs. generativists using misleading language or quietly revising their positions over time. Jun 2, 2018 at 17:53
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    See also the comments on the answers here for some other people's understanding of this argument: What's the difference between recursion and embedding? Jun 2, 2018 at 17:56

You can look at Universal Dependencies, also SIL's list of Grammatical categories

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