Grammar Info

N5 Lesson 1: 9/12


い-Adjective meaning 'good'

よく can also mean 'frequently/often', and has several different potential kanji


Non-Past Form: いい
Non-Past Negative Form: よくない
Past Form: よかった
Past Negative Form: よくなかった


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About いい

いい is an adjective that means 'good' in Japanese. It can be a little bit difficult to use at first, as it conjugates differently to other い-Adjectives.

In these sentences, we can see that the first い in いい changes to よ, depending on the form. This is unique to いい, and does not happen with other adjectives.

いい can sometimes be seen as (), in these cases, the kanji is likely to be read as よい, and not いい. There is technically no difference between these two meanings, but よい does sound more formal/old-fashioned.


When used as an adverb, よく should not be confused as a conjugation of いい. よく has several possible kanji that it may stem from, and means frequently/often/well.




    (It is) good.


    This is good.


    This is a good book.


    This is also a good book.


    This is a good sound.

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いい – Grammar Discussion

Most Recent Replies (13 in total)

  • ggenya


    A little confused on the conjugation of this topic.

    Does using ’いい’ require the the use of ’だ’ or ’です’?
    For example, I noticed in the first example we do in fact use ’だ’,
    However, the ‘だ’ is dropped in further examples that use the post form (positive and negative).

    So, is the conjugation imply the ‘is’ portion?
    Do we need to use "だ " in the present tense affirmative case? ,
    Eg, would これはいい映画えいが be a valid sentence (as opposed to これはいい映画えいがだ)

    Let me know if I’m thinking about this the right way or if may questions make sense.

    Thank you.

  • nekoyama


    The だ in this sentence has nothing to do with the いい. The いい just modifies 映画 so we’re talking about a “good movie” instead of just a “movie”. You can treat いい映画 as a noun phrase, it could be replaced with anything else that can act as a noun (such as just 映画 by itself), and the rest of the sentence wouldn’t change. That there is a だ in this sentence is because it’s a typical AはBだ type of sentence.

    In many of the other examples, いい is the main clause’s predicate, e.g. これは良くない. In that case, adding だ is not grammatical.

    In the question sentences for this grammar point you’ll sometimes see です added after よくない or よかった etc. This is a special exception for です, where it doesn’t have a grammatical function, and only acts as a “politeness particle”. But this is only possible with です, we can’t use だ in those cases.

  • ggenya


    Thank you for clarifying that! です as a politeness article was throwing off my understanding.

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