Unmarked

An unmarked term, in linguistics, is one which is used in a general sense, as opposed to a specific sense. For example, "man hour" refers to the amount of work one person can do in one hour. It does not specify a male human being, despite protestations by feminist language reformers. The term "person hour" has accordingly not gained currency.

A road sign saying "men at work" does indeed employ the connotation of big, burly, heavily-muscled male human beings. That is the sort of worker typically employed in heavy construction. The point of the sign is to prompt the necessary caution by drivers, alerting them to the presence of construction workers along or on the road. A phrase like "people at work" would fail at this purpose, because it connotes shopkeepers and secretaries. You might as well say "downtown area".

A term like "teacher" is often understood to mean a female person. Indeed, writers have often used feminine pronouns in a sentence using the unmarked term. This is, of course, not to imply that men cannot be teachers. It merely reflects the stereotype which teacher invokes. "Nurse" even more strongly implies a woman, so much so that the term "male nurse" must be used to indicate a man. No one says "female nurse".

A vehicle like a bus (short for "omnibus") meant a horse-drawn carriage in the 1860s. The unmarked term could hardly refer to anything else, as only trains had a powerful enough engine to pull cars. A "bus" nowadays can only be an automobile. Likewise, a "car" would be part of a chariot or (later in history) a train. Now the unmarked term refers to an automobile other than a bus or truck. Only in context of rail travel or elevators would "car" mean anything else.