弱い
よわい
yowai
= weak
弱い (yowai) is the everyday adjective for weak — but it stretches much further than physical strength. It covers being bad at something, being unable to handle it, and things being faint or low in intensity, making it one of the most useful adjectives to really understand.
At its core, 弱い is the opposite of 強い (tsuyoi, strong): 力が弱い (physically weak), 弱いチーム (a weak team), 電波が弱い (a weak signal). But its most idiomatic use is the pattern 〜に弱い, which usually means ‘bad at handling’ or ‘unable to cope with’ something. お酒に弱い means you can’t hold your liquor; 暑さに弱い means you can’t stand the heat; 数字に弱い means you’re bad with numbers.
That same 〜に弱い can also mean ‘has a weakness for’ in the sense of being unable to resist — 甘いものに弱い (‘a sucker for sweets’) — or ‘vulnerable to’ — この素材は水に弱い (‘this material is not water-resistant’). Context decides which shade applies, but the thread is always ‘weak against / can’t handle’.
弱い also combines with 気 and 体 for character and health: 気が弱い (ki ga yowai) means timid or faint-hearted, while 体が弱い (karada ga yowai) means physically frail or sickly. As a regular i-adjective it conjugates predictably — 弱くない (not weak), 弱かった (was weak), 弱くなる (to become weak).
Master 〜に弱い early — it is everywhere. お酒に弱い is far more natural than a literal ‘I can’t drink much’, and misreading it as ‘weak toward alcohol’ in the wrong direction can confuse you; it means alcohol easily overwhelms you.
Distinguish 気が弱い from 体が弱い: the first is a timid personality, the second is a frail body. They share 弱い but describe completely different kinds of weakness.
Since it’s an i-adjective, don’t add だ before nouns in the plain style — say 弱いチーム, not 弱いだチーム, and conjugate the 〜い ending directly (弱くて, 弱かった).
Everyday use
私はお酒に弱いので、一杯で顔が赤くなります。
Watashi wa osake ni yowai node, ippai de kao ga akaku narimasu.
I can’t handle alcohol, so my face goes red after one drink.
Casual / Social Media
気が弱くて、嫌なことをなかなか断れない。
Ki ga yowakute, iyana koto wo nakanaka kotowarenai.
I’m timid, so I have a hard time refusing things I don’t want to do.
Formal / Cultural context
この地下はWi-Fiの電波が弱いですね。
Kono chika wa Wi-Fi no denpa ga yowai desu ne.
The Wi-Fi signal is weak down here in the basement, isn’t it?
弱い anchors the well-known four-character phrase 弱肉強食 (jaku-niku-kyou-shoku), literally ‘the weak are meat; the strong eat’ — the Japanese equivalent of ‘survival of the fittest’. It appears in talk about business, sports, and nature, showing how 弱い frames not just individuals but whole systems of competition.
The culture’s discomfort with openly displaying weakness surfaces in the expression 弱音を吐く (yowane wo haku, ‘to voice weak sounds’, i.e., to whine or admit you can’t go on). Since perseverance is highly valued, 弱音を吐く carries a faint sense of giving in, and enduring without it is often praised — a mindset visible in school clubs, workplaces, and sports.
Modern Japanese also plays with mental toughness through the pair 打たれ弱い and 打たれ強い — literally ‘weak/strong when hit’ — meaning emotionally fragile versus resilient under criticism or setbacks. Describing someone as 打たれ弱い is a common, everyday way to say they bruise easily under pressure, extending 弱い neatly from the body to the spirit.