These words refer to someone who acts for himself or others. At its most general, performer may indicate the one who carries out an action: the performer of a double somersault. It may also indicate someone who can accomplish tasks or attain goals: children who are poor performers in school. In these senses, the word can also apply to inanimate objects: a report specifying those cars that were the best performers . On a more particular and less formal level, the word is much more widely used to indicate any sort of entertainer: clowns, acrobats and other circus performers . Doer has no widely used specific sense, unlike performer , and is even less frequently used in its corresponding general sense: separating mankind into the doers and the dreamers. An archaic idiom survives, however, in modern usage: a doer of good works. In this sense it has slightly derogatory overtones. The word can also be used positively to describe one who gets on with things enthusiastically: good old Jim – he’s real doer .

Executive at its most formal can refer to someone who actually does a job, either on his own behalf or for others; this is best illustrated by the compound nouns of certain titles. An executive director is one who actually directs the work of his group, although someone else may have the honorary tide of director. In its most common use, executive indicates a person who belongs to the beat-paid upper bracket of a business, the one concerned with decision-making; executives who rank high enough in the firm to have a private office with a window.

Agent refers to a person who does something, against a commission, on behalf of someone else. Businessmen, authors and actors all may hire agents to conduct their affairs.