These words all mean to have an effect upon a person’s behaviour thinking or feelings. Influence is to bring about a change in another’s actions or thoughts by persuasion, example or action, often of an indirect sort: influenced by a high-school biology teacher to take up the study of medicine; influencing workers to produce more goods by praising them and bettering their working conditions.

In this context affect means to have an effect on another’s feelings.

• He is always deeply affected by Handel’s music; Fear affects some people by making them powerless to act.

Influence and affect may both be used of things that tend to respond to outside stimuli or actions. Influence is usually used in this sense of intangible forces, and affect of physical ones: to influence public opinion through the press; to affect the size of a crop by using fertilizer. Affect may sometimes imply an undesirable reaction: Unusual exertion may affect the heart.

Impress means to affect deeply and lastingly: impressed by a man’s prodigious talent; impressed by his first sight of the Eiffel Tower.

Sway means to change another’s opinions or feelings successfully in a deliberate way. It is a stronger word than either influence or affect . The word implies the sue of control or irresistible persuasion, often combined with the weakness of the one swayed : to sway a dissatisfied minority group by impassioned political speeches full of promises; a man so swayed by public adulation that he snubs his old friends.