I mean, by this phrase, its fitness or efficiency to or for the accomplishment of the purposes for which it is used.

As it is the nature of an agent, to be the doer of something, so it is the nature of an instrument, to be that with which something is effected.

To make signs, is to do something, and, like all other actions, necessarily implies an agent; so all signs, being things by means of which other things are represented, are obviously the instruments of such representation.

Words, then, which represent thoughts, are things in themselves; but, as signs, they are relative to other things, as being the instruments of their communication or preservation.

They are relative also to him who utters them, as well as to those who may happen to be instructed or deceived by them.