「買う」 (kau) means "to buy." It's a common transitive verb used when you acquire something by paying money. You typically use the particle "を" to indicate the object you are purchasing, like buying food or tickets.

「買(か)う」はお金(かね)を払(はら)って物(もの)を手(て)に入(い)れる動詞(どうし)です。「〜を 買(か)います」と使(つか)います。