Affect vs. effect

"Affect" is usually a verb, while "effect" is usually a noun. The usage of these words gets confusing when the words are used in unusual ways, but this rule of thumb is helpful in most circumstances.

"The program takes effect in March." This sentence uses "effect" as part of a verb phrase meaning "is put in place." Another usage is to state a cause-effect relationship. "The effect of the program will be felt in March."

By far the most common usage of "affect" is as a verb. "The program affects many Las Vegans." One way to remember the difference is that "affect" actually means "to cause an effect," in a way.

"Affect" can also be a noun meaning an emotional state or appearance: "His affect was grave." However, this is an uncommon usage, and it is usually pronounced differently, with emphasis on the "a."