What type of clause is 「蛙飛び込む」 in the famous haiku by Basho?


Usually, Basho's famous haiku, when written with a translation, is presented
thus:

> 古池や  
>  蛙飛び込む  
>  水の音

And translated roughly (similar to three out of five translations available in
[Wikisource](https://en.wikisource.org/wiki/Frog_Poem)):

> An old pond  
>  A frog leaps  
>  The sound of water

However, there are inversions of order of the last two lines, as was brought
to my attention in [a recent post I made in the Literature Stack
Exchange](https://literature.stackexchange.com/questions/2024/why-are-haiku-
usually-of-17-syllables#comment3609_2027):

> An old pond  
>  The sound of water  
>  As a frog leaps in/Of a frog leaping in

Here, the second line is modified by the third, whereas in the first, they
stand separate.

In Japanese, what type of clause is the phrase 「蛙飛び込む」 in this haiku?




Grammatically 蛙飛び込む modifies 水の音 as a relative clause. It's not that 水の音
modifies 蛙飛び込む. [Japanese is an almost pure head-final
language](https://en.wikipedia.org/wiki/Head_\(linguistics\)#Head-
initial_vs._head-final_languages), which means a modifying part almost always
comes before a modified part.

This relative clause is a bit special, and it's a bit hard to give a very
literal translation of 蛙飛び込む水の音. This is called a gapless relative clause
described [here](https://japanese.stackexchange.com/a/14550/5010), or type C
relative clause described
[here](https://japanese.stackexchange.com/q/39551/5010). Basically 蛙飛び込む
explains what kind of 水の音 we are dealing with. One rather literal translation
would be "the sound of water of/from a frog's leaping in." Although this one
is grammatically closer to the original haiku, it doesn't look similar to the
original in terms of line order. So neither is definitely better than the
other.




Grammatically 蛙飛び込む modifies 水の音 as a relative clause. It's not that 水の音
modifies 蛙飛び込む. [Japanese is an almost pure head-final
language](https://en.wikipedia.org/wiki/Head_\(linguistics\)#Head-
initial_vs._head-final_languages), which means a modifying part almost always
comes before a modified part.

This relative clause is a bit special, and it's a bit hard to give a very
literal translation of 蛙飛び込む水の音. This is called a gapless relative clause
described [here](https://japanese.stackexchange.com/a/14550/5010), or type C
relative clause described
[here](https://japanese.stackexchange.com/q/39551/5010). Basically 蛙飛び込む
explains what kind of 水の音 we are dealing with. One rather literal translation
would be "the sound of water of/from a frog's leaping in." Although this one
is grammatically closer to the original haiku, it doesn't look similar to the
original in terms of line order. So neither is definitely better than the
other.

