In English, one little letter can make a big difference. Take compliment (praise) and complement (something that completes something else), or principal (main, primary; or, head of a school) and principle (fundamental truth or basis of belief). These pairs are homophones — words that sounds alike but have different spellings and different meanings.

Perhaps the most commonly confused homophones are affect and effect. Consider these sentences from student writing this semester:

“I think that had a big affect on my ability and desire to lead people as a group and do things together,” she said.

Maybe these pictures will have some affects on the people who view them.

Both writers meant effect. The two words sound exactly alike in normal speech (unless an English teacher is exaggerating the pronunciation to make a point). International students needn’t feel too bad if they don’t know the difference; most Americans don’t, either. Part of the reason is that, with affect and effect, it’s not a simple matter of one’s being a noun and one’s being a verb; either can be either.

Here’s a chart to help you understand when to use which.

(Thanks, Dictionary.com, for the definitions.)

Here’s hoping this chart will help you use affect and effect effectively — that is, with the desired result.