Learning to spot whether a word is a noun, adjective, or verb is one of the fastest ways to improve your Japanese reading and speaking. Below are simple rules, quick tests, and real examples you can use right away.

1) Quick mental model

• Nouns = people, places, things, ideas. They usually sit with particles (は/が/を/に/で) and often pair with です／だ when used as predicates.

• Verbs = actions or states that change. They appear in dictionary form (plain form) like いく, たべる, のむ and can be conjugated (ます、た、ない、て form…).

• Adjectives = describe nouns. Two main kinds: い-adjectives (end in い) and な-adjectives (use な before a noun).

2) Fast tests you can use in a sentence

Try each test with the unknown word:

• Particle test (works for nouns & verbs):

If the word can take a particle like を (object) or が (subject) directly before/after it in a natural way, it is likely a noun (with は/が) or a verb (with を before the verb).

Example: ねこをさわる → ねこ is a noun (object marker を + verb さわる).

• Conjugation test (works for verbs and い-adjectives):

Put the word into a verb-like conjugation: add ます (polite) — if it sounds natural, it’s a verb.

Change ending to くない (negative) — if that works, it’s an い-adjective.

Example: たべる → たべます (verb). たかい → たかくない (い-adjective).

• です / な test (works for nouns and な-adjectives):

Attach です after the word: if it becomes a natural predicate, it’s either a noun or a な-adjective.

If the word needs な before a noun (しずかなへや), it’s a な-adjective.

Example: しずかです (na-adj). がくせいです (noun).

• Modifier test (before a noun):

If the word goes directly before a noun to describe it, check how it connects:

い-adjectives attach directly: おおきいいえ.

な-adjectives use な: しずかなへや.

Verbs use the plain form + noun after them (relative clause): たべるひと (the person who eats).

3) Common tricky case: words ending in る

• Many verbs end with る (たべる, みる). Some adjectives or nouns might also end with る in roman letters, but true adjectives rarely end in る in their い-form.

• Use the conjugation test: try ます form + negative form. If たべる → たべます works, it is a verb. If it doesn’t conjugate like a verb, try the adjective tests.

4) Short checklist you can run quickly

• Can it take particles like は/が/を/に/で? → noun (or verb if particle before it is を).

• Can you say X ます naturally? → verb.

• Does it end in い (and change to くない)? → い-adjective.

• Does it need な before a noun, or sound natural with です? → な-adjective or noun.

• Can it appear directly before a noun? Check whether it needs な or attaches directly.

5) Examples (Japanese in ひらがな, with romaji and English)

• ねこがいる

romaji: neko ga iru

English: A cat exists.

→ ねこ = noun (marked by が); いる = verb.

• たかいくるま

romaji: takai kuruma

English: an expensive car

→ たかい = い-adjective (ends in い), modifies noun くるま.

• しずかなへや

romaji: shizuka na heya

English: a quiet room

→ しずか = な-adjective (uses な before noun).

• えいごをはなす

romaji: eigo o hanasu

English: to speak English

→ えいご = noun (object with を); はなす = verb.

• がくせいです

romaji: gakusei desu

English: (I am) a student.

→ がくせい = noun; です is the copula.

• おいしいたべもの

romaji: oishii tabemono

English: tasty food

→ おいしい = い-adjective describing noun たべもの.

6) Practice suggestions (daily routine)

• Read short sentences and underline the particle or conjugation that gives away the word type.

• Memorize common い-adjective endings (〜い) and common な-adjectives (きれい、しずか、べんり etc.).

• Practice conjugating verbs to ます / ない / た / て forms — verbs are recognized by conjugation.

• Make flashcards with the word, its particle/context example, and the label (noun/adjective/verb). Context helps you remember the role.

7) Final tips — how to decide fast when you’re unsure

• When unsure, look at the grammar around the word (particles and auxiliary words like です/ます). Those nearby words almost always reveal the role.

• Learn the most common patterns rather than trying to memorize every exception. Japanese gives lots of clues through particles and conjugation — use them.

Start practicing with short sentences, and after a week you’ll notice you spot nouns, verbs, and adjectives much faster.

How to tell nouns, adjectives, and verbs apart in Japanese — a short guide for learners