The sentence I came up with was:


So essentially I was using がち to say how students "tend to/have a tendency to" sleep less. My 先生 said I used it wrong, without giving proper advice. Any help would be appreciated!

1 Answer 1


[V ます-stem]-がち works as a な-adjective. So you begin with a verb phrase and end up with a な-adjective.

Your sentence appears to have started from this verb phrase.

x 睡眠時間を短くする寝ます

This is syntactically wrong because it has two verbs with no proper connector.

Let’s use the first verb.


From this you get the following correct sentence.


〜がち being an adjective, you can use it attributively, too.


短く寝がち (without 睡眠時間を) is grammatical but not idiomatic because the original verb phrase 短く寝ます is not idiomatic. 遅く寝ます is better with focus on the time you go to bed (i.e. start to sleep), rather than the duration.


  • Thank you for your anwser! But I have a question: I've seen some forms of [V ます-stem]-がち+ , which means [V ます-stem]-がち is like a noun, right? If we see 寝がち as a single nuon, then 睡眠時間を短くする寝がち wouldn't be grammatical?
    – shepherd
    Commented May 29, 2023 at 8:49
  • 1
    @shepherd - の may be used instead of な but it's still an adjective. (There are things called の-adjectives.) 睡眠時間を短くする寝がち is ungrammatical for the reason I explained. And it makes no sense even if 寝がち was treated as a stand-alone noun.
    – aguijonazo
    Commented May 29, 2023 at 9:26
  • Thanks, I understand. I think that the reason for the existence of の-adjectives is due to some な-adjectives having noun-like stems. For example, in the dictionary, "必要" is both the stem of a な-adjective and a noun. Therefore, if it makes sense semantically, we can also add noun modifiers such as the verb's 連体形 in front of it. Here, I tend to believe that the word "寝がち" itself has no meaning and it only becomes meaningful when we treat the phrase "睡眠時間を短くする寝ます" as a whole verb and attach "がち" to it. However, as you mentioned, 睡眠時間を短くする寝ます is wrong, so 睡眠時間を短くする寝がち is ungrammatical.
    – shepherd
    Commented May 29, 2023 at 10:56
  • @shepherd - Another thing is that 〜がち doesn't mean "tendency". It describes the way something has a tendency. 必要 on the other hand can mean "necessity" (必要性). It's more noun-like. 睡眠時間を短くする寝がち makes no sense semantically even if we accepted it as syntactically valid.
    – aguijonazo
    Commented May 29, 2023 at 11:28
  • Yes, I often separate "semantic" and "syntactic". In my opinion, if the stem of a な-adjective can be attached by "の", it means it's also a noun grammatically("の-adjective" is not a formal term in my textbooks), however, the nuon-like stem maybe limited semantically, so it cannot be freely used in sentenses like nuons. Also here as 〜がち can be attached by "の" in some situations, I will think of it also as a 名詞性接尾辞 and accept "[睡眠時間を短くする]寝がち" as syntactically valid(verb's 連体形+nuon), but because of ~がち's meaning you said, the phrase does make no sense semantically.
    – shepherd
    Commented May 29, 2023 at 12:02

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