LESSON NOTES · レッスンノート

N4Lesson notes · Sep 30, 2026

Strong and weak in Japanese: 強つよい, 弱よわい, and the に that turns them into skills

強つよい (tsuyoi) means strong and 弱よわい (yowai) means weak — but the moment you add に, as in 数字すうじに強つよい or お酒さけに弱よわい, they stop describing muscle and start describing how well you handle something.

English uses "strong" for a lot of things: strong people, strong coffee, strong wind, strong in math, strong feelings. Japanese splits them across several words, and the split is where learners get tripped up. This article sorts out which word goes where.

The basics

What do 強つよい and 弱よわい mean?

They are い-adjectives that describe power, force, or strength, and their opposites. They work for people, animals, forces of nature, and abstract things.

あの人ひとは強つよい。 — That person is strong. (neutral, fighting or physical strength) 今日きょうは風かぜが強つよいですね。 — The wind is strong today, isn't it? (polite, small talk about weather) この猫ねこは体からだが弱よわい。 — This cat is physically weak. (neutral, meaning frail or sickly rather than "can't lift things")

Note that 体からだが弱よわい is not "weak muscles." It means someone gets sick easily. 体からだが強つよい is the opposite, a person who rarely gets ill.

What does 〜に強つよい mean?

〜に強つよい means "good with X" or "resistant to X." The に marks the thing you are strong against or strong in. This is one of the most useful patterns for anyone who wants to say what they are good at without sounding stiff.

彼かれは数字すうじに強つよい。 — He's good with numbers. (neutral, praising a skill) この傘かさは風かぜに強つよい。 — This umbrella stands up to wind. (neutral, a product description) 私わたしは寒さむさに強つよいです。 — I handle cold well. (polite, about your own constitution)

The sense is "won't be beaten by it." That is why 数字すうじに強つよい feels a little different from 数学すうがくが得意とくい — it suggests someone who can work with figures easily and reliably, not just someone who enjoys or scores well at math. If you want the fuller comparison of 得意とくい, 上手じょうず, 苦手にがて, and 下手へた, see good at and bad at in Japanese.

What does 〜に弱よわい mean?

〜に弱よわい has two meanings: "bad with X" and "can't resist X." Which one you get depends on what X is.

私わたしはお酒さけに弱よわいです。 — I can't handle alcohol. (polite, low tolerance) 彼女かのじょは押おしに弱よわい。 — She gives in when people push. (neutral, a personality note) 甘あまいものに弱よわくて、つい食たべちゃう。 — I have a weakness for sweets, so I end up eating them. (casual, a guilty confession)

Physical things like お酒さけ or 暑あつさ give you "low tolerance." Emotional or social things like 押おし (pushing) or 涙なみだ (tears) give you "a soft spot for it." Both are the same grammar: something gets past your defenses.

Beyond the basics

What is the difference between 強つよい and 濃こい for coffee?

Japanese does not say 強つよいコーヒー for strong coffee. It says 濃こいコーヒー (koi kō (koi khī (koi kh). 濃こい means dense, thick, or concentrated, and it is the word for flavor, color, and makeup. Its opposite is 薄うすい, thin or weak.

このコーヒー、濃こいね。 — This coffee is strong. (casual, comment on a cup) お茶ちゃが薄うすすぎる。 — The tea is too weak. (neutral, a complaint) 濃こい味あじが好すきです。 — I like strong-flavored food. (polite, about taste)

強つよい does show up with things you feel or sense hitting you: 匂においが強つよい (a strong smell), 光ひかりが強つよい (strong light), and even 強つよいお酒さけ for hard liquor. But for how concentrated a drink or a taste is, use 濃こい. For more on that side of the vocabulary, our taste words article covers 濃こい and 薄うすい in context.

How do you say "sturdy" — is that 強つよい?

Not usually. For objects and bodies that hold up under wear, Japanese prefers 丈夫じょうぶ (jō (jbu) or 頑丈がんじょう (ganjō (ganj). 丈夫じょうぶ is a な-adjective and it means durable, sturdy, or healthy.

このカバンは丈夫じょうぶだ。 — This bag is sturdy. (neutral, a review) うちの子こは丈夫じょうぶで、あまり風邪かぜをひかない。 — My kid is hardy and rarely catches colds. (casual, a parent talking) この箱はこ、頑丈がんじょうだね。 — This box is really solid, isn't it? (casual)

頑丈がんじょう is a heavier, more solid feeling than 丈夫じょうぶ. 丈夫じょうぶ is the everyday word.

How do you turn them into nouns?

Add さ to make 強つよさ (strength) and 弱よわさ (weakness). To be specific about what kind, Japanese has separate words: 強つよみ (tsuyomi) is a strength or selling point, and 弱よわみ (yowami) or 弱点じゃくてん (jakuten) is a weakness.

この選手せんしゅの強つよさは、あきらめないところだ。 — This player's strength is that they never give up. (neutral, sports commentary) 弱点じゃくてんを教おしえて! — Tell me your weak spot! (casual, in a game or fight) 面接めんせつで自分じぶんの強つよみを聞きかれた。 — I was asked about my strengths in the interview. (neutral)

弱点じゃくてん is very common in anime and games: a monster's weakness, an opponent's blind spot. 弱よわみ also means "a weakness someone can use against you," as in 弱よわみを握にぎる, to have something on someone.

What about 強つよくなる and 最強さいきょう?

To become strong or weak, use the なる pattern: 強つよくなる and 弱よわくなる. The same rule applies to any い-adjective, so if you want the full explanation, see くなる and になる.

もっと強つよくなりたい。 — I want to get stronger. (casual, the classic shounen line) 雨あめが強つよくなってきた。 — The rain has gotten heavier. (neutral, a change in progress)

最強さいきょう (saikyō (saiky) is 最さい plus 強きょう, the superlative "strongest." It is everywhere in anime: 最強さいきょうの魔法使まほうつかい, 最強さいきょうのチーム. Its opposite is 最弱さいじゃく (saijaku), the weakest, which is used both as a joke and as a rank in game-like worlds. To see how 最さい and 一番いちばん compare, read Japanese superlatives.

お前まえが最強さいきょうだ。 — You're the strongest. (casual, masculine, hero talk) 最弱さいじゃくの職業しょくぎょうだと思おもわれてた。 — It was thought of as the weakest class. (casual, a common fantasy setup)

Can 強つよい and 弱よわい describe a personality?

Yes, with 気き. 気きが強つよい means strong-willed or headstrong, and 気きが弱よわい means timid or easily intimidated. Two related nouns are 強気つよき (bold, aggressive stance) and 弱気よわき (timid, pessimistic stance).

彼女かのじょは気きが強つよい。 — She's strong-willed. (neutral, can be a compliment or a warning) 試合前しあいまえなのに弱気よわきなことを言いうなよ。 — Don't say weak stuff right before the match. (casual, coach or friend) 強気つよきに出でる。 — To take a hard line. (neutral, negotiation or fights)

気きが強つよい is a mixed bag. Depending on the speaker it can mean admirably tough or hard to deal with. Listen to the tone.

How to practise it

The easiest exercise is to collect "strong and weak with X" in your daily life. Every time you notice yourself handling something well or badly, put it in Japanese: 辛からいものに強つよい, 早起はやおきに弱よわい, 人ひとごみに弱よわい. You will be using the に pattern within a day.

For coffee, tea, flavor, and color, make it a habit to reach for 濃こい and 薄うすい first, and only switch to 強つよい if it truly hits your senses. When you watch anime, count how many times you hear 最強さいきょう versus 強つよい, and notice which one belongs to a person and which one to a wind or a smell.

Common mistakes

  • Saying 強つよいコーヒー for strong coffee. Use 濃こいコーヒー. 強つよい is understandable, but it sounds like the coffee hits you rather than that it is concentrated.
  • Using 強つよい and 弱よわい as if 〜に and 〜が were interchangeable. 数字すうじに強つよい is a fixed way to praise someone's skill with numbers. 数字すうじが強つよい is not natural.
  • Reading 体からだが弱よわい as "physically weak." It says the person gets sick easily, not that they lack muscle.
  • Using 丈夫じょうぶ for a person's strength in a fight. 丈夫じょうぶ is for sturdiness and health. For someone who wins fights, use 強つよい.
  • Mixing up 弱点じゃくてん and 弱よわみ. 弱点じゃくてん is a weak spot in a thing or a fighter. 弱よわみ is a weakness in someone's situation or character that could be exploited.

Strong and weak: English to Japanese

English Japanese Use for
strong (person, fighter) 強つよい power, fighting ability
strong wind, strong smell 風かぜが強つよい / 匂においが強つよい intensity you feel
strong coffee, strong flavor 濃こい concentration, thickness
sturdy, durable 丈夫じょうぶ / 頑丈がんじょう objects, healthy bodies
good with X Xに強つよい skill, resistance
bad with X, can't resist X Xに弱よわい low tolerance, a soft spot
strength, strong point 強つよさ / 強つよみ ability / selling point
weakness, weak spot 弱よわさ / 弱よわみ / 弱点じゃくてん fragility / exploitable / target
strong-willed, timid 気きが強つよい / 気きが弱よわい personality
the strongest 最強さいきょう anime, games, rankings

FAQ

Is 数字すうじに強つよい the same as 数字すうじが得意とくい? Close, but not identical. 得意とくい focuses on what you are good at and confident with. 〜に強つよい suggests you handle it reliably and it does not defeat you. In everyday speech they overlap heavily, and either is fine for praising someone.

Can I say 私わたしは日本語にほんごに強つよいです for "I'm strong in Japanese"? It is grammatical, but it sounds like a boast, and it can imply unusually high reliability. For a normal learner, 日本語にほんごが得意とくいです or 日本語にほんごを勉強べんきょうしています is more natural. Also, saying it about yourself is less modest than saying it about someone else.

How do I say "weak in Japanese" as a learner? 日本語にほんごが苦手にがてです is the natural choice. 日本語にほんごに弱よわい is possible, but it sounds like a permanent weak spot rather than "I find it hard right now." See the good at and bad at article for how 苦手にがて and 下手へた differ.

What is the difference between 強つよい酒さけ and 濃こい酒さけ? 強つよい酒さけ is liquor that is high in alcohol by nature, like whisky or shochu drunk straight. 濃こい is for a mixed drink with a lot of alcohol in it: このハイボール、濃こいね means the bartender was generous with the whisky. So a drink can be 濃こい, but the liquor itself is 強つよい.

Is 弱よわい rude? Calling a person 弱よわい can be an insult, especially about fighting or character, as in 弱よわい奴やつ. About things like 体からだが弱よわい it is just a description, though it can feel blunt, so people sometimes say 体からだがあまり丈夫じょうぶじゃない instead.

Practice

Build each answer before opening it. Questions 3 and 4 are a pair, and so are 5 and 6.

1. Say "I can't handle alcohol" in polite Japanese.

Show answer

お酒さけに弱よわいです — に marks what you are weak against, and 弱よわい gives the "low tolerance" sense.

2. Say "He's good with numbers."

Show answer

彼かれは数字すうじに強つよい — 〜に強つよい is the "good with X, not beaten by X" pattern.

3. Say "This coffee is strong" (concentrated).

Show answer

このコーヒーは濃こい — for concentration, thickness and flavor, Japanese uses 濃こい, not 強つよい.

4. Say "The wind is strong today."

Show answer

今日きょうは風かぜが強つよい — the wind hits with force, so 強つよい is right. Compare with question 3: same English word "strong," two different Japanese words.

5. Say "This bag is sturdy."

Show answer

このカバンは丈夫じょうぶだ — 丈夫じょうぶ is for objects that hold up, not 強つよい.

6. Say "That fighter is strong."

Show answer

あの人ひとは強つよい — for fighting power, 強つよい is the word. 丈夫じょうぶ would mean sturdy or healthy, which is a different idea. This is the pair to question 5.

7. What does 体からだが弱よわい mean?

Show answer

Someone who gets sick easily — it describes a frail constitution, not weak muscles.

8. Say "I want to become stronger."

Show answer

強つよくなりたい — 強つよい drops い, adds くなる, then たい for "want to."

9. What is the difference between 弱点じゃくてん and 強つよみ?

Show answer

弱点じゃくてん is a weak spot; 強つよみ is a strength or selling point. Anime says 弱点じゃくてんを突つく to hit a weak spot, while interviews ask about 強つよみ.

10. Which fits a person who never backs down, 気きが強つよい or 気きが弱よわい?

Show answer

気きが強つよい — 気き means spirit or will, so 気きが強つよい is strong-willed and 気きが弱よわい is timid.

数字すうじに強つよい and お酒さけに弱よわい are easy to read and trickier to produce, so in a trial lesson, try お酒さけに弱よわい on yourself and 数字すうじに強つよい on a friend, and hear which of the several "strong" words fits.

Vocabulary from this article

Tap the block to select all of it, then copy. In Anki: File → Import, note type Basic, separator Tab — the first column becomes the front, the second the back.

強い	つよい — strong
弱い	よわい — weak
数字	すうじ — numbers
お酒	おさけ — alcohol
寒さ	さむさ — cold (noun)
押し	おし — pushing, pressure
濃い	こい — strong, dense, dark (flavor, color)
薄い	うすい — thin, weak (flavor, color)
丈夫	じょうぶ — sturdy, healthy
頑丈	がんじょう — solid, robust
強さ	つよさ — strength
強み	つよみ — strong point
弱点	じゃくてん — weak point
最強	さいきょう — the strongest
最弱	さいじゃく — the weakest
気が強い	きがつよい — strong-willed
気が弱い	きがよわい — timid
強気	つよき — bold stance
弱気	よわき — timid stance

I'm Yuuki, a Japanese teacher based in Tokyo. I've taught on italki as a Top 1% teacher and watched over 1,500 anime, so most of the example sentences on this blog come from lines I've actually heard students ask about — including this one, where the same English word "strong" splits into three or four Japanese words. For practice with feedback, Book a trial lesson · $13, or work through Japanese practice exercises first.

Sources: the author's own lessons and standard reference grammars.

More drills like the ones above, plus a timed JLPT-style mock test: Practice · N4 · Read something at this level: JLPT N4 stories with audio

More “Describing Things: Japanese Adjectives & Opposites” articles →

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