Has anyone created an exposition detailing the phonotactics of English in a way which would be easy for a human to understand but also rigorous enough for it to be possible to program a piece of software with the information to look at any given word written in IPA and say whether it's "allowed" in English or not?

Just to make sure I'm using this term correctly: For example, in English /fr/ is allowed, such as in "friend". However, /vr/ is not allowed. The phonotactics of a language describe which sound sequences are allowed and which aren't.

Note: Such a description would differ between different dialects. Any such description, no matter the dialect, would be helpful for me.

2 Answers 2


See this related question for relevant discussion.

This has not been done, and there is ample reason to hold that in principle it cannot be done. The premise underlying the question is that there is a crisp cognitive mechanism that tells us that a certain string "is allowed" or "is disallowed", but there is no reason to believe in such a function. The strongest case for some kind of template function that can be made is for defining what a "syllable" is in English, which means what a possible onset, nucleus and coda are.

There is not much serious doubt that it is a systematic fact of English grammar that clusters of obstruent plus oral sonorant are possible in English onsets and that oral sonorant plus obstruent are not possible, thus play is a word, and lpay could not be one. Within that class of "allowed" clusters, some of the predicted sequences don't appear at the expected rate, so voiced fricatives plus liquid are almost non-existent. Examples such as "zloty" all come from foreign languages, though English speakers can pronounce them with no problem, if they happen to know the words. See G.N. Clements & S.J. Keyser CV Phonology and E. Selkirk "The syllable" for accounts of sequencing principles within the syllable. The Clements & Keyser model distinguishes between positive conditions and negative filters, and while positive conditions absolutely must be obeyed, negative filters might admit of exceptions and tend to generate weaker speaker reactions. So for example, labial+labial onsets are very rare, and there are no Germanic words in English with onset *pw, but there are some Spanish-derived words (pueblo, Puerto Rico for those who don't pronounce the latter Porto Rico). There are only 2 words with onset [zw] and most people don't known either word (zwieback, Zwicky). The problem is, there is no way to tell if the described sequences simply don't happen to exist, or are actually explicitly excluded. If your theory of phonotactics says that "doesn't exist" is the same thing as "isn't allowed", then [flænt] would be disallowed for everybody, and [marʌm] is disallowed for everybody except those people acquainted with the word. Since there is no valid test of "is allowed" for words, there isn't a possible list of strings that are cleanly "in" vs. "out". You can probably devise an operational test such as a certain minimum score on a 5-point Likert scale for speaker reactions, but that will not actually give you a precise partitioning of strings of English phonemes.

  • Another simple example is /lg/ as a coda. My (admittedly non-native) intuition tells me it can't be nearly as wrong as, say, /vr/ onset is, but I can't think of a single word that'd attest it (unless you'd be willing to count Golgotha, and syllabify it appropriately). As a side-note, an imperfect but handy list of attested syllables can be found here: semarch.linguistics.fas.nyu.edu/barker/Syllables/index.txt
    – user54748
    Dec 11, 2015 at 6:36
  • /vr-/ isn't so bad as all that. Every anglophone child with a toy train or motorcycle can say /vrum vrum/ without devoicing, hesitation or epenthesis long before they learn other languages. Granted, onomatopoeia and expressive words generally can in general break phonotactics in many languages (cf. meh), but this is a word kids learn from other kids, i.e. directly acquired.
    – John Cowan
    Jan 3, 2021 at 23:32
  1. Benjamin Lee Whorf proposed a description of the possible English monosyllables in 1940 -- the paper is in Language, Thought, and Reality.

  2. Morris Halle gave an elegant (though probably wrong) theory based on his "simplicity metric". That was in his paper "Phonology in Generative Grammar". In order to economize on the feature specifications in the lexicon, we formulate Morpheme Structure Rules (MSRs) that let us abbreviate lexical entries by filling in omitted specifications. We must stop writing new MSRs when the feature specs in all the MSRs come to equal the saved features in lexical entries; that is the point of diminishing returns. Then the admissible morphemes are those morphemes which would not be altered by the application of any MSR.

  3. David Stampe's Natural Phonology makes the admissible words those which would not be changed by any of the universal processes that remain unsuppressed in adult speech. (Processes are suppressed during the course of language acquisition when their application would prevent children from pronouncing adult forms accurately.)

  4. My idea about admissibility is that it cannot be connected directly with the words actually in the lexicon of a language, because it is perfectly normal for those to include many recently borrowed words which do not fit the phonemic pattern of the language at all.

All of these proposals are programmatic, and none meets your criteria that they be programmable and comprehensible. Except perhaps Whorf's (but it's only for monosyllabic words).

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