Conjugating い-Adjectives to Negative Form

    • Adjective
    • Conjugation Form
    When an い-adjective ends in 〜くない, it tells us that the word is negative, or not hot, not cold, not sweet, not spicy, etc. The negative suffix ない can be switched out for ありません for a more formal context.

    What Is くない?

    〜くない is the negative form ending for い-adjectives. It replaces the 〜い on the end of an adjective to indicate that the adjective is negative, or "not true." So while 難しい means "is-difficult," 難しくない means "is-not-difficult." Hopefully after reading this, you'll feel the latter is true about using 〜くない!

    While 〜くない itself creates the negative form, it's actually made up of two components: the くform and ない. To take an い-adjective from its present positive form to its く form, you drop the 〜い ending and replace it with 〜く. This allows the い-adjective to stick to another word, in this case, ない. Let's see how this works with an actual adjective:

    難し + く + ない = 難しくない

    Piece of cake, right?

    くなかった : The Past Tense Form of くない

    〜くなかった is the past tense negative form of い-adjectives.

    If you've read our page on the positive form of い-adjectives, you'll know that the 〜い on the end of an adjective is what marks the word as present tense. If 〜くない can show the present tense with its final 〜い, it can also change to show the past tense. To get there, we remove the final 〜い and add the past tense suffix 〜かった. Let's try this out with our example adjective, 難しい:

    難しくな + かった = 難しくなかった

    Now let's see it in a full sentence:

    • トーフグのおかげで、日本語の試験は難しくなかった
    • Thanks to Tofugu, the Japanese test wasn't hard.

    Other Forms of い-Adjectives

    Check out the chart below to see how 〜くない fits into the い-adjective paradigm. Click on other conjugations or forms to learn more about them!

    Form 日本語 English
    Stem Form
    く Form strongly
    て Form くて strong, (and)
    Present Tense Form is-strong
    Past Tense Form かった was-strong
    Negative Form くない is-not-strong
    Past Negative Form くなかった was-not-strong
    Conditional Form ければ if strong...
    Measurable Noun Form strength
    Subjective Noun Form strong point