What are the rules regarding "mute vowels" ("u" after "s" and "i" after "sh")?


When you first begin to learn Japanese you are taught that Japanese has no
stress and each syllable should be pronounced equally.

You also learn that certain vowels are not pronounced, or only pronounced very
slightly, such as the "u" in "desu" and the "i" in "deshita".

But it seems that sometimes these vowels are pronounced if they occur in the
first syllable of a word such as "sugoi", "subarashii", "shiro", "shimbun".

Is this a kind of exception to both rules or is it just something a foreigner
might think they hear which is not really there?




I have a book in my university library that has a 100-odd page article
dedicated to these mute vowels, and it still doesn't seem to give a complete
picture. So unfortunately, this feature of Japanese phonology is quite
complex.

Still, there's a rather simple rule of thumb that can point you to most of the
places where muting _may_ occur (and in most of them it does occur, most of
the time :)). It goes like this:

  1. The vowel must be a short `i` or `u`.
  2. The consonant before the vowel must be [voiceless](http://en.wikipedia.org/wiki/Voiceless):  
`/k/`, `/s/` (also includes しゅ), `/t/`, `/h/` (ふ and ひ), and maybe also `/p/`
(though it seems rarer).

  3. The vowel must be at the end of a word, or followed by another voiceless consonant.

This explains why you see muting in s **u** koshi and h **i** kari but not in
s **u** goi and b **i** kkuri.

Another useful thing to remember is that you can't have two muted vowels in a
row, so in words s **u** ki and ts **u** kush **i** ta not all vowels that
match rule 1-3 become mute.

## Edit:

I should have given more than a passing mentions to the exceptions, because
they are quite many. The rules I've given cover _most_ of the occurrences of
muted vowels, and by 'most' I don't mean 99%. It's probably not even 80%,
though I'm only giving rough guesses here.

So here are some exceptions:

  * `[bikkrishta]` for びっくりした is quite common.
  * Sometimes (in really fast speech) some very specific grammatical forms get their vowels elided, even when the vowels are not `/u/` or `/i/`. For instance, わからない can be shortened to `[wakarnai]`. It usually goes further than that with /r/ assimilating to the /n/, and thus you get the わかんない which you very often find in writing.
  * Tsuyoshi Ito and Kdanski have mentioned `[sbarashii]` `[sgoi]` in the comments.

There are of course many more. This is just an example why this issue is
complex.




I have a book in my university library that has a 100-odd page article
dedicated to these mute vowels, and it still doesn't seem to give a complete
picture. So unfortunately, this feature of Japanese phonology is quite
complex.

Still, there's a rather simple rule of thumb that can point you to most of the
places where muting _may_ occur (and in most of them it does occur, most of
the time :)). It goes like this:

  1. The vowel must be a short `i` or `u`.
  2. The consonant before the vowel must be [voiceless](http://en.wikipedia.org/wiki/Voiceless):  
`/k/`, `/s/` (also includes しゅ), `/t/`, `/h/` (ふ and ひ), and maybe also `/p/`
(though it seems rarer).

  3. The vowel must be at the end of a word, or followed by another voiceless consonant.

This explains why you see muting in s **u** koshi and h **i** kari but not in
s **u** goi and b **i** kkuri.

Another useful thing to remember is that you can't have two muted vowels in a
row, so in words s **u** ki and ts **u** kush **i** ta not all vowels that
match rule 1-3 become mute.

## Edit:

I should have given more than a passing mentions to the exceptions, because
they are quite many. The rules I've given cover _most_ of the occurrences of
muted vowels, and by 'most' I don't mean 99%. It's probably not even 80%,
though I'm only giving rough guesses here.

So here are some exceptions:

  * `[bikkrishta]` for びっくりした is quite common.
  * Sometimes (in really fast speech) some very specific grammatical forms get their vowels elided, even when the vowels are not `/u/` or `/i/`. For instance, わからない can be shortened to `[wakarnai]`. It usually goes further than that with /r/ assimilating to the /n/, and thus you get the わかんない which you very often find in writing.
  * Tsuyoshi Ito and Kdanski have mentioned `[sbarashii]` `[sgoi]` in the comments.

There are of course many more. This is just an example why this issue is
complex.

