v. 1
To influence or alter.
The experience affected me deeply.
v. 2
To make a show of; to put on a pretense of; to feign; to assume. To make a false display of.
to affect a British accent
v. 3
To move to emotion.
He was deeply affected by the tragic ending of the play.
v. 4
Of an illness or condition, to infect or harm (a part of the body).
Hepatitis affects the liver.

Related words

Word family: affectibility affectingly affected affectedness affectation affection affectionate affective
Phrases: pseudobulbar affect labile affect

Forms

Past participle: affected
e.g. affected → regarded, concerned, related, involved…

Choose the right word

Affect, Takes, Feign, Pretend or Assumes?

If he takes to himself the credit and appearance of qualities he does not possess, he is said to affect or feign, or to pretend to, the character he thus assumes.

J. C. Fernald, English Synonyms and Antonyms (1914)

Example sentences

concern Money is without a doubt my most pressing concern.
involve Dear woman, why do you involve me? Jesus replied.
relate I see no reason why he doesn't relate to the firm.
pertain This discussion does not pertain to you.
influence Such magazines have a great influence on children.
alter As the artist grows older his paintings may alter.

Popularity over time

Word	1850 → 2019	Trend
affect		steady
concern		steady
involve		steady
relate		steady
pertain		steady
influence		steady

Use in printed books, per decade from 1850 to 2019.

By length

4 letters: like¹, make¹, work¹, move¹, fake¹, harm¹, melt¹
5 letters: color², touch¹, adopt², alter², feign¹
6 letters: change¹, impact², strike¹, assume², colour², regard², relate², modify³
7 letters: concern², involve², pretend², pertain², impinge²
8 letters: interest², simulate³
9 letters: influence³, transform²

The small number after each word is its number of syllables (color² = 2 syllables).

In other languages

Français: affecter
Italiano: adibire
Español: afectar
Deutsch: treffen