Here’s the straight-out-of-the-box dictionary definition:
a general philosophical theory of signs and symbols that deals esp. with their function in both artificially constructed and natural languages and comprises the three branches of syntactics, semantics, and pragmatics.
—Webster’s Third New International Dictionary. 1981.
And now for a little anecdote showing how a simple word change can make a great difference.
Years ago I was working as a proofreader in a type shop when an ad came across my desk. The last paragraph of the copy began with a boldface lead-in reading: America believes... .
I was new on the job, and I queried the client’s usage of the word, “America,” suggesting in its place “Americans.” The client made the change and the ad ran. It was only after I saw the ad in print that I realized how egregious an error I had made.
No one is really interested in what Americans do. What is really being alluded to here is the concept of America. And that concept is far more ambiguous and open to interpretation than “Americans.”
The client’s copywriter had it right the first time.
The force of the ad was intended to reflect the notion that not only was everyone buying the product but also that the democratic principle of freedom of choice was being exercised in the process.