The word **邀请函** (yāoqǐng hán) is a compound noun formed through semantic combination, where the first element **邀请** means "to invite" (composed of 邀, "to solicit," and 请, "to request"), acting as a modifier that specifies the purpose, and the second element **函** means "letter" or "document," indicating the physical medium. Together, they create a head-final structure typical in Chinese, literally translating to "invitation letter" or "letter of invitation," where the modifier "邀请" describes the type of document denoted by the head noun "函."