The Writing Center @ The University of Wisconsin - Madison
The Writer's Handbook
An Editing Checklist

11. Words easily confused

"Effect" is most often a noun (the effect), and "affect" is almost always a verb.

Other pairs commonly confused: "lead"/"led" and "accept"/"except."

Check a glossary of usage to find the right choice.

Incorrect:

The recession had a negative affect on sales.

Correct:

The recession had a negative effect on sales.
(or) The recession affected sales negatively.

Incorrect:

The laboratory instructor chose not to offer detailed advise.

Correct:

The laboratory instructor chose not to offer detailed advice.