For any given language, its phonotactics defines which sounds can apear in which positions and combinations, in which syllables, in which sorts of words, playing which roles. Languages vary widely in this respect – in:
- Whether all syllables begin with a consonant or whether they allow syllables to begin with a vowel, as in arm and ark;
- Whether no syllables have a consonant after the vowel or whether this is allowed, again as in arm and ark;
- How they allow consonants to combine with other consonants in what are known as ‘clusters’ before and after vowels, as in cry and elm;
- How they allow vowels to combine with one another in what are known as diphthongs, as in oh and why;
- How far they allow parts of sounds to combine as in the first and last sounds of church and judge, beginning with a complete closure and ending in an only partial closure in what is known as an affricate;
- Whether and how far they allow relatively complex sounds like affricates to combine with other sounds, as in squelch;
- Whether and how far they allow consonants to double or ‘geminate’ as in between the adjacent N sounds in non-native and unknowing, where native and knowing are fine on their own unless they are turned into their opposites by non and un, neither of which count as words on their own; so this is very restricted in English;
- Whether what are (almost universally) considered to be ‘long’ vowels in English, as in arm and eat, would be better considered as geminates (they aren’t so considered because the short variants don’t exist; the short vowels all differ from the closest long vowel in at least one way other than length);
- How they allow vowels and consonants to combine in syllables, feet, and what we think of as ‘words‘.
This is known as the ‘phonotactics’.
English is uncommonly permissive in most, but not all. of these respects. But on many of them the evidence of the spoken language is not clear. English contrasts tip, ship and chip. So Chip could have an initial T SH cluster. If that was the correct analysis TSIP, beginning like tsunami, pronounced with a T and S, would also be predicted as a possible word, complicating the phonotactics.
English also has many commonly occurring sequences between the beginnings and ends of words, as in hop scotch, which could easily be misheard as single words. The fact that hop carries a stress, marking it as an independent word, is easily missed. And the sequence PSK could be miscontrued as the beginning or ‘onset’ of a syllable, as in children’s occcasional pronunciations of spaghetti as PSKETI. The small child learning English has to resolve the issues here on the basis of unclear evidence.
Some languages, particularly the Slavonic languages and the languages of the Caucasus, allow very complex clusters. Some West African languages have complex sounds like both G and B together, as in the name of the language Igbo. In English by contrast the G and B in egg box and dog basket are sequenced, at the end of one word and at the beginning of the next, and not simultaneous as in Igbo,
The words, strength, strange, scrounge and change would not count as possible words in many languages. Such languages would disallow the STR and SCR and NG combinations and the final TH in strength, the way the GE is preceded by an N and the fact that the vowel begins and ends with the tongue in different positions in the mouth in strange, and scrounge and the CH and GE which use different airstreams at the beginning and the end of the sound in change.
The complexities of English phonotactics and the fact that on the simplest analysis English STR, SCR, and SPR are sequences of phonemes rather than single, complex phonemes, is obviously something which children learning English have to learn from evidence which is not obvious or simple.