法定 (fǎdìng) is an adjective meaning 'prescribed by law' — it describes something set by official statute (e.g. age, holiday, procedure). Unlike 合法 (héfǎ, 'lawful, legal'), which evaluates whether an action complies with the law, 法定 focuses on what the law itself dictates. 依法 (yīfǎ) is an adverb meaning 'according to law', used with verbs.