What does affect mean?
Affect is most commonly a verb meaning to influence or produce a change in someone or something: weather affects crops, news affects markets, kindness affects people deeply. It is neutral in tone, applying equally to beneficial and harmful outcomes, and it appears constantly in journalism, science, and everyday speech. A second, older verbal sense means to pretend or put on a manner — to affect indifference, for instance — though this usage is now relatively formal. In psychology, affect also functions as a noun denoting the outward expression of emotion, as when clinicians describe a patient's mood as showing 'flat' or 'blunted' affect. The word derives from Latin afficere, 'to act upon,' via the past participle affectus. It is famously confused with effect, its near-homophone: affect is typically the action, effect the result. Mastering this distinction is one of the most practical wins in English usage.
To have an effect on; to make a difference to someone or something. A secondary sense means to pretend to feel or display a quality one does not genuinely have.
"The drought severely affected the region's harvest."
In the 'pretend' sense, affect takes a noun complement: 'He affected a British accent.'
In psychology, the experience or observable expression of emotion or feeling.
"The clinician noted the patient's flat affect during the interview."
This noun is pronounced with stress on the first syllable (/ˈæfɛkt/) and is used almost exclusively in clinical and academic contexts.
Psychologists can diagnose depression partly from a patient's 'affect' — whether their emotional expression looks flat, blunted, or appropriate to what they're saying.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of affect
Affect comes from Latin afficere, meaning 'to do something to' or 'to act upon,' formed from ad- ('toward') plus facere ('to make or do'). Its past participle, affectus, gave English both the verb and, through later psychological usage, the noun. The same root produced affection, affectation, and affective, which share the core idea of something acting upon the mind or feelings. The word entered English in the late Middle English period, with the 'pretend' sense developing in the early modern era.
Related word forms
How affect is actually used
As a verb, 'affect' is standard in both formal and informal writing and carries no strong connotation — it is neutral about whether the change is positive or negative. The 'pretend' sense is somewhat formal and less common today. The noun sense belongs mainly to clinical and academic psychology and would sound out of place in everyday conversation.
Easily confused with affect
Affect is usually the verb meaning to influence something, while effect is usually the noun meaning the result or outcome of a change.