The sound /ʃ/ is almost always spelled with more than one letter i.e. with a digraph unlike, say, /p/ which is spelled with a single letter (pan, pen, pie). I have noticed a particular pattern: vowels before digraphs are usually short and not long (or diphthongs). The /ʃ/ sound is spelled with a digraph so I assume the vowel before "sh" is usually short. Other sounds such as /p/ (shape), /t/ (hate), /k/ (make) and even /tʃ/ (aitch) can occur after /eɪ/.
Also notice that /-eɪk/ is never, in my opinion, spelled with -ck.
It may seem to be confusing spelling and pronunciation but both of them are closely related to each other. If English allows /eɪʃ/ in the end of the same syllable (or in the end of a word), then it might be possible to have a long vowel/ diphthong before the digraph "sh". However, I haven't been able to find any word in which /ʃ/ is spelled with a digraph and has a long vowel/ diphthong before it which led my to my question:
- Does English allow /eɪʃ/ in the same syllable?