TOOL 工具, a small tool used in work such as science or medicine
〔科学、医学等工作用的小巧的〕器械，器具:
surgical instruments
外科（手术）器械
乐器;
electronic instruments
电子乐器
FOR MEASURING 用于测量, a piece of equipment for measuring and showing distance, speed, temperature etc
仪器，仪表:
a failure of the flight instruments
飞行仪表的失灵
sensitive earthquake-detecting instruments
灵敏的地震探测仪
METHOD 方法, [usually singular] something or someone that is used to get a particular result
促成某事的物（人）; 手段，方法:
Interest rates are an important instrument of economic policy.
利率是经济政策的重要调控手段。
Good management should be an instrument for innovation.
良好的管理应当是促成创新的手段。
FOR HURTING 用于伤害, something that is used to hit or hurt someone
〔伤害他人的〕工具:
Death was due to a blow on the head with a blunt instrument .
死亡是由于钝器击中头部所致。
instrument of fate / God, [literary] someone or something that is used by a power beyond our control