Japanese -i and na-Adjectives (Romaji Only)

If you’re like me and mostly want to speak Japanese, not read or write it, this post is for you. Everything here is written in romaji (the Romanized version of Japanese). If you’re interested in learning hiragana, katakana, or kanji, I recommend using other resources, or even asking ChatGPT for a custom plan.
(Feel free to check out the r/languagelearning and r/LearnJapanese subreddits for extra resources or recommendations).

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What Are -i and na-Adjectives?

Japanese adjectives fall into two main categories:
✅ -i adjectives (end in い)
✅ na-adjectives (require な before a noun)

These are used to describe everything; people, places, feelings, and objects. Each type conjugates differently.

⚠️ Watch out! Some na-adjectives look like -i adjectives (especailly if you rely on romaji for Japanese) (like kirei or kirai), but aren’t. The only way to be 100% sure is by learning them with exposure or seeing them in kana/kanji.

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Don’t worry about learning how and why these conjugate this way, this page is mainly just to expose you to what -i and na-adjectives are, and importance of them.

🌟 -i (い) Adjectives

These end in the hiragana い (i) and conjugate by changing the -i directly.

Common Examples:

• Kawaii – cute
• Samui – cold
• Atsui – hot
• Takai – tall/expensive
• Chiisai – small
• Ooki – big

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✅ Present Positive (Informal):

Just use the adjective as is.

Examples:

• Kono neko wa kawaii. – This cat is cute.
• Tenki wa samui. – The weather is cold.

✅ Present Positive (Formal):

Add desu after the adjective.

Examples:

• Kono inu wa yasashii desu. – This dog is nice.
• Kino no Tenki wa samui desu. – It was cold yesterday.

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❌ Present Negative (Informal):

Drop the final -i and add -kunai.

Examples:

• Ooki → ookikunai – not big
• Chiisai → chiisakunai – not small
• Takai → takakunai – not tall/expensive

Sentence Examples:

• Ano ie wa ookikunai. – That house isn’t big.
• Kono hon wa takakunai. – This book isn’t expensive.

❌ Present Negative (Formal):

Add desu:

• Ookikunai desu – It’s not big.
• Samukunai desu – It’s not cold.

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🔁 Past Positive (Informal):

Drop -i, add -katta.

Examples:

• Kawaii → kawaikatta – was cute
• Atsui → atsukatta – was hot

Sentence Examples:

• Ano inu wa kawaikatta. – That dog was cute.
• Kino wa atsukatta. – Yesterday was hot.

🔁 Past Positive (Formal):

Add desu:

• Kawaikatta desu – It was cute.
• Atsukatta desu – It was hot.

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❌ Past Negative (Informal):

Take the negative form (-kunai), drop the -i, and add -katta: → -kunakatta

Examples:

• Warui → warukunakatta – wasn’t bad
• Yasui → yasukunakatta – wasn’t cheap

Sentence Examples:

• Eiga wa tanoshikunakatta. – The movie wasn’t fun.
• Kono mise wa yasukunakatta. – This store wasn’t cheap.

❌ Past Negative (Formal):

Add desu:

• Tanoshikunakatta desu
• Yasukunakatta desu

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🌟 Na (な) Adjectives

Na-adjectives don’t conjugate directly. Instead, the “na” is kept when placed before nouns, dropped otherwise, and changed in conjugation depending on the sentence.

Common Examples:

• Kirei na – pretty / clean
• Suki na – to like
• Genki na – healthy / lively
• Kantan na – easy
• Benri na – convenient

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✅ Before a Noun:

You must include na between the adjective and the noun.

Examples:

• Kirei na hana – a pretty flower
• Shizuka na hito – a quiet person
• Anzen na basho – a safe place

Sentence Examples:

• Kirei na hana wo mitsukeitai. – I want to find a pretty flower.
• Sore wa shizuka na hito – That is a quiet person.

✅ Before a Noun (Formal):

add desu:

• Kirei na hana desu
• Anzen na basho desu

✅ Present Positive Sentence (Informal):

Change na → da

Examples:

• Kirei da – It’s pretty.
• Yuumei da – (He/She/It) is famous.
• Genki da – I’m feeling good.

✅ Present Positive (Formal):

Drop na, add desu.

Examples:

• Kirei desu – It’s pretty.
• Benri desu – It’s convenient.
• Yuumei desu – He/She is famous.

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❌ Present Negative (Informal):

Change na → ja nai

Examples:

• Hima ja nai – I’m not free
• Jozu ja nai – Not good at
• Hen ja nai – Not weird

Sentence Examples:

• Gomen, kyo hima ja nai. – That dog was cute.
• Ano eiga wa hen ja nai?. – Isn’t that movie weird?

❌ Present Negative (Formal):

Change ja nai → ja nai desu or dewa nai desu (more polite)

Examples:

• Yuumei ja nai desu – It’s not a dream.
• Benri dewa nai desu – It’s not convenient.

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🔁 Past Positive (Informal):

Change na → datta

Examples:

• Taisetsu datta – was important/precious
• Tokubetsu datta – was special
• Genki datta – was healthy

Sentence Examples:

• Kesa no kaigi wa tokubestu na monodatta. – The meeting this morning was special.
• Kino otosan wa genkidatta. – Dad was happy yesterday.

🔁 Past Positive (Formal):

Change datta → deshita

Examples:

• Taisetsu deshita
• Tokubetsu deshita

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❌ Past Negative (Informal):

Start from ja nai, drop -i, add -katta → ja nakatta

Examples:

• Suki ja nakatta – didn’t like
• Taihen ja nakatta – wasn’t difficult
• Heta ja nakatta – wasn’t bad

Sentence Examples:

• Nigai no mono wa suki ja nakataa. – I didn’t like bitter things.
• E wa heta ja nakatta. – I didn’t suck at drawing.

❌ Past Negative (Formal):

Multiple politeness levels:

1. Ja nakatta desu
2. Dewa nakatta desu (more polite)

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🔤 English/Loan Words = Always Na-Adjectives

Loan words (borrowed from English and other languages) are always considered na-adjectives in Japanese.

Examples:

• Modan na – modern
• Sutairisshu na – stylish
• Ereganto na – elegant

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Final Tips:

• Once again don’t stress on using yo correctly.
• Exposure and practice will help you get a feel of when to use it.
• Start noticing how yo is used in everyday phrases, anime, or J-dramas!
• Use ChatGPT for practice sentences and quizzes on using yo.

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