“Affect” and “effect” might be two of the most commonly confused words in the English language. Most people pronounce them exactly the same way; instead of using a long “a” or long “e” both of them begin with a schwa (“uh”) sound.
The difference, though, is pretty simple once you get the hang of it.
“Affect” is a verb, or an action word. One way that you can remember this is to remember that “affect” and “action” both start with the letter “a.” The verb “affect” will always take a direct object. In other words, “affect” will always be followed by a noun, or thing, that is the recipient of that action. Therefore, your sentence will always say, “affect something.”
“Effect” is a noun, or a thing. A friend recommended that I remember it this way: “the effect.” If you’re wondering whether the word in the sentence is a noun or a verb, look at the word in front of it. If “affect/effect” is preceded by a word like “the,” “an,” or “some,” it’s definitely a noun.
These are pretty hard-and-fast, simple rules, but there are a couple of caveats, especially in academic or formal writing.
In very formal writing, “effect” may be used as a verb. Whereas “affect” means to influence directly, the verb “effect” means to influence indirectly. So, you might say, “The organization hopes to effect change.” That would mean that the organization is trying to cause change to happen.
The inverse is also true. “Affect” is usually a verb, but it can sometimes be a noun. It’s used as a noun primarily in psychology or in the social sciences. It means facial expressions or demeanor. Interestingly, this is the only version that’s pronounced differently. It’s pronounced with a short “a” sound in the first syllable, so it’s “aa-fect” instead of “uh-fect.”
For the most part, though, remember that “effect” is usually a noun and “affect” is most commonly a verb.