effect

Effect is a noun meaning a change that is the result or consequence of an action, event, or condition. In science, philosophy, law, and everyday language, the term denotes what follows a cause. The phrase cause and effect expresses this relationship.

In science, notable effects include the Doppler effect, a frequency shift due to motion, and the photoelectric effect, which helped establish quantum theory. In engineering and media, effects describe observable changes produced intentionally, such as echoes or visual effects in images.

In medicine and pharmacology, effects refer to the action of a drug or treatment, including therapeutic effects and adverse effects. The placebo effect describes improvement due to expectation rather than the active agent, illustrating the role of perception in outcomes.

In economics and social science, effects denote outcomes of policies or actions, such as multiplier effects, spillovers, and feedback effects that propagate through systems over time.

In the arts and entertainment, the term covers techniques that alter perception or realism, including visual effects (VFX) and sound effects (SFX). Practical effects are achieved physically, while digital effects are computer-generated.

Language usage distinguishes effect as a noun for outcome, and affect as a verb meaning to influence. To effect means to bring about or accomplish.

See also causality, cause and effect.