買う
かう
kau
= to buy / to purchase
Kau is the first shopping verb every Japanese learner picks up, but its reach goes far past the checkout counter — the same word lets you buy anger, buy respect, and buy trouble, not just groceries.
Kau is a godan (u-verb): the dictionary form kau becomes katte in the te-form, katta in the plain past, and kaimasu in polite speech. The noun form kaimono (shopping, literally “bought thing”) is one of the most common nouns in daily Japanese, showing up in phrases like kaimono ni iku (to go shopping). What surprises learners is how far kau extends beyond physical objects: urami o kau means to incur someone’s resentment, hankan o kau means to provoke backlash or a negative reaction, and on the positive side, doryoku o kau means to value or recognize someone’s effort. In all these idioms, kau treats an emotion or reaction as something you “acquire” through your own actions — a transaction, just not a monetary one.
The biggest trap is the te-form: because kau ends in -u, beginners often guess kaute, but the correct form is katte (the u-ending group swaps to -tte, not -ute). In casual speech, katte plus shimau contracts to kacchatta, the classic guilty-pleasure confession for an impulse buy — something you didn’t plan to purchase but did anyway. Also watch the kanji: kau meaning “to buy” is 買う, while kau meaning “to keep a pet” is 飼う — identical pronunciation, completely different kanji and meaning, so context (or the kanji itself) is essential to tell them apart.
Everyday use
夕飯の材料をスーパーで買った。
Yuuhan no zairyou o suupaa de katta.
I bought the ingredients for dinner at the supermarket.
Casual / Social Media
また新しいスニーカー買っちゃった…。
Mata atarashii suniikaa kacchatta…
I went and bought new sneakers again…
Formal / Cultural context
彼の積極性を買っています。
Kare no sekkyokusei o katte imasu.
I value his proactive attitude.
Japan’s convenience store density turned kau into a verb people use a dozen times a day — a rice ball before work, a coffee at lunch, a bill payment at the register on the way home. This constant, low-friction rhythm of buying is baked into daily routine in a way that shapes how naturally the word comes up in casual conversation, far more often than “buy” tends to in a single English-speaking day.
The checkout script itself has changed with the cashless shift: IC cards like Suica and barcode-pay apps replaced a lot of coin-counting, so the physical act of kau increasingly means a tap or a phone scan rather than handing over cash. Store clerks adjusted their set phrases accordingly, but the verb underneath stayed exactly the same.
The idiomatic side of kau — buying resentment, buying backlash, buying someone’s respect — reveals something about how Japanese frames social consequences as a kind of economy. You don’t just “anger” someone or “earn” their trust; you actively “purchase” that outcome through your behavior, as if reactions were goods sitting on a shelf waiting to be acquired.