「小さい」 (Chiisai) is an i-adjective meaning 'small' or 'little'. It's used to describe something that is not large in size. It acts as a direct modifier for nouns, helping you to specify that an item or creature is small in dimension.

「小(ちい)さい」は「small, little」という意(い)味(み)のい形容詞(けいようし)です。物(もの)の小(ちい)ささを表(あらわ)します。