Using い-Adjective Negative Form (〜くない)

    • Adjective
    Use 〜くない on an い-adjectives to say that it's “not” that adjective. い-adjective 〜くない can be used immediately before a noun, or it can go at the end of a sentence.

    Table of Contents

    くない for Negation

    Using the negative suffix 〜くない allows you to say what is "not." If this is review, you might say it's 新しくない (not new) information. If, however, the information is new to you, that would be expressed with the positive form, 新しい (is new). Notice that both of these end in the present tense 〜い ending, a feature that they share.

    To get to the negative form, take the く Form of an い-adjective (by removing 〜い and adding 〜く) and combine it with the negative ない. Let's break down our example adjective to see how this works:

    • 新し +  + ない = 新しくない 
    • is-not-new

    And now, in a sentence:

    • 新しくないやつで良ければ、貸してあげるよ!
    • If you're okay with one that isn't new, then I'll lend you mine!

    Negative い-Adjectives in Sentences

    Negative い-adjectives can modify nouns in the same grammatical positions as other forms of い-adjectives. One of these positions is immediately before a noun:

    • 忙しくない
    • is-not-busy time
    • 寒くない
    • is-not-cold day

    When an い-adjective is used in a phrase like this, it modifies a noun that is playing a role in a larger sentence. For example:

    • 忙しくない時は、何をしますか?
    • What do you do when you're not busy?
      (Literally: What do you do in is-not-busy time?)

    Negative い-adjectives can also appear at the end of the sentence. In these cases, they modify the subject of the sentence, which is usually marked by particle は or が.

    • 那覇の冬は寒くない
    • Naha winters are not cold.
    • 数学の先生が優しくない
    • It's the math teacher that isn't nice.

    Making くない Polite

    Politeness in Japanese is marked at the end of a sentence with forms like です and 〜ます . If you have a sentence that ends in an い-adjective, you can level-up your politeness using these forms too.

    One option is to add です after the negative ない. This style is common in polite conversation. Let's take a look at いい (good). Note than when いい conjugates, it is always pronounced よい (and is often written with its kanji 良い):

    • くないです
    • is not good

    Alternatively, you can switch out ないです for the more formal ending, ありません. This option feels a little bit too stiff for most spoken situations, so it tends to be used more commonly in writing.

    • くありません
    • is not good (formal)

    Splitting く and ない with Particle は for Contrast

    It's easy to think of 〜くない and 〜くありません as units, but remember that they are in fact two separate components: く form + a negative word. Because of this, they can be separated by the particle は to give a nuance of contrast.

    • 美味しくない
    • not delicious (but…)
    • 美味しくありません
    • not delicious (but…)

    To paint a clearer picture of why you might use particle は in this place, let's examine the grammar in context. Imagine that my friend is feeling a bit sick. I just so happen to have an amazing cold remedy tea, but the problem is, it tastes horrible. When offering it to her, I might say:

    • 美味しくないけど、体にいいよ。
    • This isn't delicious, but it's good for you.

    By inserting particle は here, it creates the sense that whatever I say is going to be contrasted with something else. In this case, I contrast the taste (美味しくはない) with the health benefit (体にいい). For this reason, it's quite common for 〜くはない to appear alongside "but" conjunctions, like が and けど. However, sometimes the contrast is implied rather than explicitly stated:

    • 悪くはないよ!
    • It's not bad (but…)

    You might use this when you want to say that something isn't bad, but imply that it isn't exactly good either, without stating it explicitly. In fact, after drinking that nasty health tea, this would be a great way for my friend to respond!

    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