When you want to connect a 活用語 (inflectable word) to something else, generally
you inflect it to the 連用形 (continuative form). However, with 形容詞
(i-adjectives), there are certain times where you affix things to the 語幹
(stem) as opposed to the 連用形.

**〜そう** (Affixes to 連用形 for 動詞, but 語幹 for 形容詞.)

> 動詞： 降りそう＝「降る」の連用形＋「そう」  
>  形容詞：おいしそう＝「おいしい」の語幹＋「そう」

**〜すぎる** (Affixes to 連用形 for 動詞, but 語幹 for 形容詞.)

> 動詞： 食べすぎる＝「食べる」の連用形＋「すぎる」  
>  形容詞：高すぎる＝「高い」の語幹＋「すぎる」

My guess is that these suffixes want something "noun-like", and since the 連用形
of 形容詞 is adverbial, it doesn't work and instead the stem ended up serving
that function.

But, this is just a guess, so I'd like to know if anyone has a historical
explanation of some of these things, or more examples to make that argument
sound more convincing.
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2013-10-17T21:54:18.000
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question
grammar verbs suffixes i-adjectives renyōkei
Why do things which attach to the 連用形 of 動詞 attach to the stem of 形容詞?
The linguist Kunio Nishiyama analyzes the 連用形 of a verb as its stem, plus an
epenthetic vowel `-i` in the case of consonant-stem verbs. This makes sense
because:

  1. It appears with consonant-stem verbs, e.g. between the root `hur-` and the suffix `-sou` (振りそう).
  2. It does not appear with vowel-stem verbs, e.g. between the root `mi-` and the suffix `-sou` (見そう).
  3. It does not appear with -i adjectives, e.g. between the root `taka-` and the suffix `-sou` (高そう).

In other words, all three of these cases can be described as the suffix
attaching to the root. The epenthetic `-i` is inserted in cases where Japanese
requires that a consonant be followed by a vowel.

I'm not sure where Nishiyama presents this idea formally. I read about it in a
footnote in his workshop paper [_Japanese Verbal Morphology in
Coordination_](http://conf.ling.cornell.edu/WOSA/Nishiyama_handout.pdf) (2012)
while I was trying to research a different topic. If you read through that
handout, you can see some of the consequences of this analysis.
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2013-10-18T02:17:07.410
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2013-10-18T10:01:35.447
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answer