い/な-adj (Present Tense)

In Japanese, adjectives just like verbs — they conjugate! You can express affirmative (positive) and negative (not) forms, as well as tense (present/past). Let’s focus on the present tense for now.

🧩 There are two types of adjectives:

• な-adjectives (Often end with な (na) when modifying nouns)

• い-adjectives (end with い)

🧩 Affirmative (Positive) For

• For both types of adjectives in the affirmative present, you add です (desu):
  • い-adjective: [adjective] + です (Example: いです = It is cold.)
  • な-adjective: [adjective] + です (Example: 元気です = She is healthy.)

❌ Negative (Present Tense)

– For い-adjectives:

• Replace the final い with くない + です
• Example: さむい → さむくないです = It is not cold.
• Formal alternative: さむくありません = It is not cold.

– For な-adjectives:

• Add じゃない + です after the stem
• Example: しずか → しずかじゃないです。 = She is not healthy.
• Formal alternative: しずかじゃ ありません = She is not healthy.

❗ Special Case: いい (good)

– The adjective いい (good) is irregular:

• Affirmative: いいです = It’s good.
• Negative: よくないです = It’s not good. (The first syllable changes from い to よ)
• Formal negative: よくありません = It’s not good.

Compound adjectives containing いい follow this pattern:

• かっこいい → かっこよくないです = It’s not cool/stylish.

🌡 Degree Adverbs

• To express how much, add:
  • とても (very)
  • すごく (extremely, casual)
  • ちょっと (a little)
• Examples:
  • とてもあついです。 = It’s very hot.
  • ちょっとさむいです。 = It’s a little cold.

✏️ Notes:

• Casual vs. Formal Speech:
  • In casual conversation, です is often dropped with い-adjectives:
    さむい (informal) vs. さむいです (formal)
  • The ないです form is more colloquial, while ありません is more formal/written

• 🚫 Common Mistakes to Avoid:
  • Don’t mix patterns between adjective types:
    × さむいじゃないです ❌ (wrong structure)
    ✓ さむくないです ✅ (correct for い-adjective)
  • Don’t forget to change the irregular いい to よく in negative forms
• In Japanese grammar, we often call the stem of an adjective its “root form” or “base form” (語幹 – gokan).
  • For い-adjectives, the stem is what remains after removing the final い. Example: さむい → さむ (stem)
  • For な-adjectives, the stem is simply the adjective itself without the な. Example: 元気な → 元気 (stem)

🌟 Quick Summary