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.