Why did Japanese evolve to have a ''she'' mora instead of a ''see'' mora in さしすせそ?

Question

In the さしすせそ series, し is an exceptions to the pattern.

Is ''she'' easier to pronounce than ''see'' or why does Japanese have this feature?

Answer 1

In the さしすせそ series, し is an exceptions to the pattern.

Is ''she'' easier to pronounce than ''see'' or why does Japanese have this feature?

This comes down to the biomechanics of pronunciation. It's the same reason we say things like "tenshun" in English for the word tension.

The specific phenomenon is called "palatalization". There are two articles about this on Wikipedia, and both are relevant:

• Palatalization (sound change)
• Palatalization (phonetics)

Put simply, when you have a so-called "front vowel" -- a vowel pronounced more in the front of the mouth -- that can gradually affect the preceding consonant, eventually causing that consonant to change.

A simple example in modern English is the phrase "did you?" The ⟨ y ⟩ in "you" is sometimes called a "palatal glide", and it basically works as a front vowel. This affects the final ⟨ d ⟩ in "did", and in fast, informal speech, this shifts from "did you" to something more like "didja": that final ⟨ d ⟩ becomes palatalized, and ultimately also shifts from a stop to an affricate consonant (it gets "friction").

A similar process has happened in languages around the world. For instance, Latin had the word "centum" for "hundred", and it was pronounced like //kentum//, with a hard //k-// sound at the start. The following //e// is a front vowel, and over time, this caused a shift in that hard initial //k-//, resulting in modern Italian "cento", pronounced instead like //t͡ʃento// (where the //t͡ʃ// part is pronounced like ⟨ ch ⟩ in English words like "chain").

In Japanese, we see palatalization in a few places. し is one such example. Historical linguists theorize that this may have originally been pronounced as //si// (like English "see"), and the front vowel //i// caused the initial //s-// to palatalize, shifting the pronunciation to //ɕi// (like English "she"). Another example is ち, where again linguists theorize that this was originally //ti// (like English "tea"), and the front vowel caused a shift to //t͡ɕi// (like in English "cheese").

Historical wrinkle

Interestingly, //e// is also a front vowel, although not quite as front as //i//. It turns out that せ was also previously subject to this same palatalization as し, and せ used to be pronounced as //ɕe// (like the first three letters in English "shed"). We can tell that this used to be the case around four hundred years ago, thanks to a Portuguese-Japanese dictionary from 1603, called the Vocabvlario da Lingoa de Iapam in Portuguese and the 日葡辞書 (Nippo Jisho) in Japanese. The compilers of that dictionary always spelled せ as ⟨ xe ⟩ (as we can see in this scan on Google Books), which was (and still is) pronounced as //ɕe// or //ʃe// in Portuguese.

I'm not sure why this palatalization reversed. It might be that //e// in Japanese was pronounced more towards the front of the mouth in years past, and gradually moved further back in the mouth. Or it might be that speakers felt more need to differentiate between し and せ. Or it might have been some social or political angle, where pronouncing せ as //ɕe// came to be seen as uncool or impolite or something otherwise negative. The reasons are lost to time, from what little I can find.

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Please comment if the above does not answer your question, and I can edit to update.