Affect vs. Effect (and Other Word Pairs English Learners Mix Up)

Some of the most commonly confused words in English aren't rare or advanced at all. They're small, extremely frequent words that sound alike, look similar, or both, and the confusion has nothing to do with vocabulary size and everything to do with how easy it is to mix up two words your ear can barely tell apart.

Affect vs. effect

The reliable shortcut: affect is (almost always) a verb meaning to influence something, while effect is (almost always) a noun meaning the result of that influence. "The weather can affect your mood" versus "the weather had a noticeable effect on the crowd." The exceptions exist (effect can rarely be a verb, meaning to bring about), but the verb/noun shortcut handles the overwhelming majority of real sentences correctly.

Then vs. than

Then is about time or sequence: "I finished dinner, then went for a walk." Than is about comparison: "This word is harder than that one." They're easy to mix up because they're pronounced almost identically in fast speech, but they never do each other's job. If you're comparing two things, it's than. If you're describing what happened next, it's then.

Its vs. it's

Its is a possessive, showing something belongs to it: "the dog wagged its tail." It's is always a contraction of "it is" or "it has": "it's raining." The usual apostrophe logic (possessives use one) doesn't apply here, which is exactly why this pair trips up so many writers, including plenty of native English speakers. A quick test: if you can expand it to "it is" and the sentence still makes sense, use the apostrophe.

Why these particular pairs are so sticky

All three pairs share something: they're common enough to use constantly, which means the mistake gets repeated and reinforced rather than corrected, and they're near-identical in speech, so your ear never flags the difference the way it would for two words that actually sound distinct. Reading and writing, not listening, is where these errors get caught.

A habit that actually fixes it

Testing yourself on the pair directly, rather than passively rereading the rule, is what makes the distinction stick. Our guide for writers covers more precision-focused vocabulary habits like this one.

Reading the rule rarely makes it stick. Actually mixing one of these up in a real sentence, and getting corrected, does. A quiz is the faster way to find out where you stand.