na-adjective, noun
clever; bright; smart; intelligent
Formal or literary term describing a person, especially a child, as quick-witted and intelligent.
彼は利発な少年だ。
He is a bright boy.
利発な子供は質問が多い。
Clever children ask many questions.
賢い is the common, everyday word for 'smart' or 'wise'. 利発 is more formal and literary, often used in written descriptions or formal speech.
聡明 also means 'intelligent' and is formal, but it often implies deeper wisdom and insight, while 利発 emphasizes quick-wittedness and brightness, especially in children.
The exact derivation is uncertain. The kanji 利 (profit, advantage) and 発 (depart, emit) together suggest a sharp, quick mind. The alternative form 悧発 uses 悧 (clever), which is a rare character directly related to intelligence.