na-adjective
intentional; on purpose; deliberate
Describes an action or behavior done with clear intent, not by accident. Often used in formal or analytical contexts.
彼の行動は意図的だったと思う。
I think his actions were intentional.
意図的に情報を隠したと非難された
He was accused of deliberately hiding information.
故意 is a noun meaning 'intent' or 'willfulness', often used in legal contexts. 意図的 is an adjectival noun describing the nature of an action as intentional.
Compound of 意図 (intention) and the suffix 的 (-like, -al), forming an adjectival noun meaning 'intentional'.