affect and effect

"Affect" is usually a verb, and "effect" is usually a noun.

affect (verb):

The new deposition process affected the efficiency of the device.

effect (noun):

We measured the effect of the new process on the efficiency of the device.

These words can be confusing because "affect" can sometimes be a noun (when it denotes an emotion), and "effect" can be a verb (when it means "to bring about").

Subject

Grammar and Usage