Affect vs. Effect: How to Know the Difference

The words "affect" and "effect" are among the most commonly misused words in the English language.

Both can be used as either a noun or a verb, but affect and effect are not interchangeable because the words have different meanings. To use affect and effect correctly, you must know each definition.

What Does Effect Mean?

as a noun:

Use "effect" as a noun when you mean a change or result or the way something acts upon something else.

a phenomenon that follows and is caused by some previous phenomenon.
an outward appearance
an impression (especially one that is artificial or contrived).
(of a law) having legal validity
a symptom caused by an illness or a drug

as a verb:

produce.
act so as to bring into existence
the central meaning or theme of a speech or literary work

How to Use Effect in a Sentence

Note the subtle difference in the use of effect as a verb, which means to cause something to happen or to bring about a result.

Substitute the words "bring about" to see if you are using effect as a verb correctly.

For example:

The stimulus checks are designed to effect a better economic status for the country.

vs.

The stimulus checks are designed to bring about a better economic status for the country.

Example sentences using effect:

Noun: The change in weather was an effect of global warming.
Noun: Global warming has a detrimental effect on the weather.
Noun: Hyperbole is an overstatement or exaggeration of speech for an effect.
Verb: Protesters want to effect change in government handling of clean-up.

I love that feeling of being in love, the effect of having butterflies when you wake up in the morning. That is special. - Jennifer Aniston

What Does Affect Mean?

As a noun:

Define affect as a noun when you work in a medical or social service field.

As a noun, the word describes an aspect of behavior, or the way emotion relates to cognitive thinking.

For example:

Though the patient is coherent and oriented, his affect is inappropriately flat.

As a verb:

Affect means to have an influence on or to produce a change. The verb Affect is used to show the noun acts upon the object. From the dictionary definitions at synonym.com, Affect means:

to have an effect upon.
to act physically on
make believe with the intent to deceive
connect closely and often incriminatingly
have an emotional or cognitive impact upon

For example:

Canines, like people, can have allergies and experience allergic reactions that sometimes affect their ears.

How to Use Affect in a Sentence

Choose "affect" in most sentences requiring a verb.

Substitute the word "influence" or "change" to test if your choice makes sense:

"influence" or
"change"

For example:

"We want to see whether driving in the dark affects safety." vs.
"We want to see whether driving in the dark influences safety."

Affect vs. Effect: Tips to Choose the Right Word

For the most part, that you can use effect as a noun and affect as a verb.

When something is caused by, use effect. Think cause and effect.
When something will alter, change, or influence something else, use affect. For example, Not requiring test scores for college applicants will affect the number of high school test takers.