Conjugating い-Adjectives to Stem Form

    • Adjective
    • Conjugation Form
    The stem form of an い-adjective is the part of the word that always stays the same, no matter what conjugation it takes. It isn’t used on its own, but it is an important part of an い-adjective to be able to recognize.

    Table of Contents

    What Is the い-Adjective Stem Form?

    The stem form of an い-adjective is the part of the word that always stays the same, no matter what conjugation it takes. For example, the stem form of 安い (is-cheap) is just the kanji 安. See for yourself:

     + い   (present)
     + かった (past)
     + くない (negative)

    Not all stem forms of い-adjectives are just kanji. In some cases, like 素晴すばらしい (is-wonderful) for example, the stem form contains hiragana characters as well:

    素晴らし + い   (present)
    素晴らし + かった (past)
    素晴らし + くない (negative)

    As you can see, the stem form is 素晴らし, which contains both kanji and hiragana.

    A Few Tricky Adjectives

    Pay special attention to two following adjectives: いい (is-good) and かわいい (is-cute).

    Finding the stem form of いい is tough if you haven't been introduced to its more formal twin, よい. いい and よい mean the same thing (is-good), but よい is more commonly used in writing, whereas いい gets a lot of use in conversational Japanese. Written in kanji, both of these words can appear as 良い. So if you're following, how else besides いい can we read 良い? If you said よい, you'd be correct!

    When we remove the final 〜い from 良い to find the stem form, we're left with the kanji 良. Since this kanji can be read as both い and よ, what is the stem? This is the part to remember: in every other conjugation besides the present tense form, 良 is read as よ. Check it out:

    い / い   (present)
    かった    (past)
    くない    (negative)

    So the stem form of いい is actually .

    This is important to remember because some い-adjectives are compound words with いい built into them, such as かっこいい (is-cool). In this case, the compounded words are 格好かっこう (appearance) and いい (is-good). When かっこいい conjugates, don't forget to use よ as the stem of いい. For example, the past tense form will be かっこかった.

    One more い-adjective that might give you trouble is かわいい. Unlike かっこいい, this word is not compounded with いい, despite having two い characters on the end. When written in kanji form, 可愛い, we see that it only has one い on the end. The other い is actually part of the reading of the kanji 愛 (わい). So here's the takeaway: when removing the 〜い ending to find the stem, a common mistake is to remove both いs, resulting in the incorrect stem かわ.

    ❌ かわいい

    ⭕ かわい

    Making this mistake isn't a cute look, so don't do it! 😉

    Other Forms of い-Adjectives

    Check out the chart below to see how the stem form 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