Affect Versus Effect

(Many thanks to Grammar Girl)

What Is the Difference Between Affect and Effect?

The majority of the time you use affect with an a
as a verb and effect with an e as a noun.

Here is a cartoon to help you remember:

"But why Aardvark?" you ask. Because there's also an example to help you remember. It's "The arrows affected Aardvark. The effect was eye-popping."
It should be easy to remember that affect with an a goes with the a-words, arrow and aardvark, and that effect with an e goes with the e-word, eye-popping. If you can visualize the sentences, "The arrows affected the aardvark. The effect was eye-popping," it's pretty easy to see that affect with an a is a verb and effect with an e is a noun.

When Should You Use Affect?
Affect with an a means "to influence," as in, "The arrows affected Ardvark," or "The rain affected Amy's hairdo." Affect can also mean, roughly, "to act in a way that you don't feel," as in, "She affected an air of superiority."

When Should You Use Effect?
Effect with an e has a lot of subtle meanings as a noun, but to me the meaning "a result" seems to be at the core of all the definitions. For example, you can say, "The effect was eye-popping," or "The sound effects were amazing," or "The rain had no effect on Amy's hairdo."
Common Uses of Affect and Effect
Most of the time affect with an a is a verb and effect with an e is a noun. First, the mnemonic involves a very easy noun to help you remember: aardvark. Yes, if you can remember aardvark -- a very easy noun -- you'll always remember that affect with an a is a verb and effect with an e is a noun. Why? Because the first letters of "a very easy noun" are the same first letters as "affect verb effect noun!" That's a very easy noun. Affect (with an a) verb effect (with an e) noun.