【Mean】 ,  【instrument】 ,  【instrumentality】 ,  【agent】 ,  【agency】 ,  【medium】 ,  【organ】 ,  【vehicle】 ,  【channel】  denote a person or thing through or by which work is performed or an end is effected.

【Mean】 , usually in the form means which may be either singular or plural in construction, is the most general of these words; it may be applied not only to persons and to such concrete things as implements, tools, and machines, but also to their actions or operations; it may also be applied to methods, policies, devices, and strategies.

【Instrument】 is applied especially to persons who merely carry out another’s will or intention, often as tools, sometimes as dupes.

When applied to concrete things,  【instrument】 often derives connotations from its musical sense (as susceptibility to manipulation and responsiveness to touch or use).

【Instrumentality】  is interchangeable with means but not with  【instrument】 because its chief implication is effective action by, or effective use of, the 【instrument】 .

【Agent】 is applied chiefly to persons and only by extension to things; the term usually names the one who does the work as distinguished from the one who wills, plans, or orders.

When applied to a thing,  【agent】 names what effects a desired result or serves as a cause producing a definite effect.

【Agency】 , like  【instrumentality】 , is not usually interchangeable with its related noun ( 【agent】  ) for it names the activity or operation of the 【agent】 or of something used to produce an effect. It is distinguished from  【instrumentality】 by its implication of causative, as opposed to effective, activity.

【Medium】 is more often applied to things than to persons; it designates especially a substance or material through which something, usually something intangible, is conveyed from one person or thing to another or given objective form.

An  【organ】 is a part or representative that performs a particular function or accomplishes a particular end or presents a particular point of view (see under JOURNAL ).

A  【vehicle】 is a 【medium】 that serves to carry and especially to carry effectively something which is to be revealed through it.

A  【channel】 is a 【medium】 that provides either an outlet or a fixed course through which something may flow from one to another.