n.有效性；效力
I doubt the effectiveness of the medicine. 我懷疑這種藥的有效性。
Once a contract is signed, it has legal effect. 合同一旦簽署即具有法律效力。
When I was sad, music had a therapeutic effect. 我悲傷的時(shí)候,音樂有治療效力。
n.低效率；無(wú)效
