To act; to exert power or strength, physical or mechanical. External bodies operate on animals by means of perception. Sound operates upon the auditory nerves through the medium of air. Medicines operate on the body by increasing or diminishing organic action.

To act or produce effect on the mind; to exert moral power or influence. Motives operate on the mind in determining the judgment. Examples operate in producing imitation. The virtues of private persons operate but on a few - . A plain convincing reason operates on the mind both of a learned and an ignorant hearer as long as he lives.

In surgery, to perform some manual act in a methodical manner upon a human body, and usually with instruments, with a view to restore soundness or health; as in amputation, lithotomy and the like.

To act; to have agency; to produce any effect.

To effect; to produce by agency. The same cause would operate a diminution of the value of stock