The word 无效 is formed by directly combining two meaningful characters: 无 (wú), meaning "without" or "lack of", and 效 (xiào), meaning "effect", "efficacy", or "result". The formation is a straightforward conceptual fusion where the first character negates the second, creating the compound meaning of "without effect" or "ineffective". It is a logical, semantic construction where the sum of the parts transparently conveys the whole idea.