na-adjective
intentional; deliberate; purposeful
Describes an action or state that is done on purpose, with conscious intent. Often used in formal or written contexts.
彼の行動は有意的だった。
His actions were intentional.
有意的なミスは許されない。
Deliberate mistakes are not tolerated.
故意 is a noun meaning 'intention' or 'willfulness', often used in legal contexts, whereas 有意的 is an adjectival noun describing the quality of being intentional.
Compound of 有意 (yūi, 'meaningful, significant') + 的 (-teki, '-like, -al'). The exact historical derivation is uncertain, but the word follows a common pattern of forming adjectival nouns from Sino-Japanese compounds.