Why many words (nouns?) end with つ？


Why many words (nouns?) end with つ？ Some examples include
寝室{しんしつ}、万年筆{まんねんひつ}. Is there some underlying patterns or rules that Japanese
language learners should be aware of?




I can answer for the examples given. We have to go back to their origin as
Sino-Japanese terms, and in particular to their Chinese pronunciation. Now I
can't actually go back to the Middle Chinese pronunciation the Japanese
reading reflects, but
[Wiktionary](http://en.wiktionary.org/wiki/Appendix:Baxter-
Sagart_Old_Chinese_reconstruction) may.

In any case, if you take the final characters, you can see on [the MDBG
Chinese to English Dictionary](http://www.mdbg.net/chindict/chindict.php) they
are pronounced `sat1` and `bat1` respectively in Cantonese. **The`-tsu` is the
reflex of the final `-t` of the imported Chinese sound. I think that will
cover many of the words you have in mind.**

If this does not convince you because of the different vowel, think of going
to [the Tawan Min Nan Common Usage Words'
Dictionary](http://twblg.dict.edu.tw/holodict_new/index.htm), being careful to
look for the _Chinese traditional form_ of the character, as you will not find
it if you look for a simplified or Japanese form. There you find the Min Nan
pronunciation, which is `pit` for the second example, so the vowel is fixed.
Strangely, the first example turns to `sik`.

But the Wiktionary comes in there and reconstructs `syit` for a Middle Chinese
pronunciation, with a fanqie (i.e. initial-final-tone explanation) that has 質
as final, read `tsit` in Min. Now a final `-t` gets turned into `-tsu` or
`-chi` (`-tu` or `-ti` once, I guess) in Japanese (e.g. `nichi`/`nitsu`, 日,
presently read `nyit` in Hakka).

As Wikipedia explains:

> fanqie is the explanation of the pronunciation of a character by giving:
>
>   1. A character with the same initial consonant
>
>   2. A character with the rest of the syllable (i.e. all other sounds and
> the tone) identical
>
>   3. A character marking this is a fanqie.
>
>

>
> For example, a modern fanqie for 日 would be 让是切: first character for the r-,
> second for the -ì, third marking the fanqie style of explanation used.

Expanding any further would have to investigate sound changes in Chinese and
Japanese, which I certainly can't do and might bring us off-topic, so I hope
this is enough for you. Btw this also answers a question like "why are there
many words ending with -pu/-fu/-bu" or "… ending with -ku/-gu", if any such
should arise, or at least starts: final stops in Chinese are -t, -p and -k.




I can answer for the examples given. We have to go back to their origin as
Sino-Japanese terms, and in particular to their Chinese pronunciation. Now I
can't actually go back to the Middle Chinese pronunciation the Japanese
reading reflects, but
[Wiktionary](http://en.wiktionary.org/wiki/Appendix:Baxter-
Sagart_Old_Chinese_reconstruction) may.

In any case, if you take the final characters, you can see on [the MDBG
Chinese to English Dictionary](http://www.mdbg.net/chindict/chindict.php) they
are pronounced `sat1` and `bat1` respectively in Cantonese. **The`-tsu` is the
reflex of the final `-t` of the imported Chinese sound. I think that will
cover many of the words you have in mind.**

If this does not convince you because of the different vowel, think of going
to [the Tawan Min Nan Common Usage Words'
Dictionary](http://twblg.dict.edu.tw/holodict_new/index.htm), being careful to
look for the _Chinese traditional form_ of the character, as you will not find
it if you look for a simplified or Japanese form. There you find the Min Nan
pronunciation, which is `pit` for the second example, so the vowel is fixed.
Strangely, the first example turns to `sik`.

But the Wiktionary comes in there and reconstructs `syit` for a Middle Chinese
pronunciation, with a fanqie (i.e. initial-final-tone explanation) that has 質
as final, read `tsit` in Min. Now a final `-t` gets turned into `-tsu` or
`-chi` (`-tu` or `-ti` once, I guess) in Japanese (e.g. `nichi`/`nitsu`, 日,
presently read `nyit` in Hakka).

As Wikipedia explains:

> fanqie is the explanation of the pronunciation of a character by giving:
>
>   1. A character with the same initial consonant
>
>   2. A character with the rest of the syllable (i.e. all other sounds and
> the tone) identical
>
>   3. A character marking this is a fanqie.
>
>

>
> For example, a modern fanqie for 日 would be 让是切: first character for the r-,
> second for the -ì, third marking the fanqie style of explanation used.

Expanding any further would have to investigate sound changes in Chinese and
Japanese, which I certainly can't do and might bring us off-topic, so I hope
this is enough for you. Btw this also answers a question like "why are there
many words ending with -pu/-fu/-bu" or "… ending with -ku/-gu", if any such
should arise, or at least starts: final stops in Chinese are -t, -p and -k.

