Affect is a verb – “to affect” – meaning to influence or have an impact on something. Effect is the noun – “an effect (a positive or a negative effect) is the result of being affected by something.

Is it have an effect or affect?

Affect is usually a verb meaning "to produce an effect upon," as in "the weather affected his mood." Effect is usually a noun meaning "a change that results when something is done or happens," as in "computers have had a huge effect on our lives." There are exceptions, but if you think of affect as a verb and effect as ...

Did the cold affect or effect you?

The verb affect means “to act on; produce an effect or change in” as in The cold weather affected the crops (it produced a change in the crops … probably killing them). ... So, when you're looking to use one of these two terms to express an action, chances are you're looking for affect.