IELTS grammar: Commonly Confused Words

Confused-word errors are unusual among grammar mistakes because they rarely make a sentence ungrammatical — "the policy will effect small businesses" is a perfectly well-formed sentence, just using the wrong word. That's exactly why examiners notice them: the sentence reads fluently until the wrong word lands, at which point it signals that a candidate hasn't fully internalised a distinction native and highly proficient writers make automatically. These pairs are worth memorising as a fixed list rather than relying on "it sounds right," since several of them sound identical or nearly identical when spoken aloud, which means the usual strategy of trusting your ear simply doesn't work for this particular category of error.

It's also worth understanding why this category of mistake persists even in candidates who are otherwise clearly at a high level: these words are often taught once, early in a learner's studies, and then never revisited explicitly, so a small initial misunderstanding calcifies into a habit that feels completely natural by the time someone is preparing for IELTS. Unlike a genuinely difficult grammar structure — which a learner usually knows they're unsure about — a confused-word error is typically produced with full confidence, which is exactly why a dedicated, deliberate check for this specific list matters more than simply "writing carefully" in general.

Affect/effect is the single most common pair on this list, and the safe default is: "affect" is a verb meaning to influence, "effect" is a noun meaning a result. "Pollution affects marine life" (verb) versus "the effects of pollution on marine life" (noun). "Effect" can rarely function as a verb meaning to bring about or cause to happen ("the new policy will effect significant change"), but this usage is uncommon enough in everyday writing that treating affect-as-verb and effect-as-noun as a fixed rule will be correct the vast majority of the time an IELTS essay needs either word.

Its/it's is a purely mechanical distinction that has nothing to do with meaning and everything to do with a single missing or present apostrophe, which is exactly why it's worth flagging separately from meaning-based confusions. "Its" is the possessive form (like "his" or "her") and never takes an apostrophe: "the company increased its output." "It's" is always a contraction of "it is" or "it has": "it's clear that output increased." A reliable test: mentally expand "it's" to "it is" — if the sentence still makes sense, the apostrophe belongs; if not, you need "its."

Then/than confuses learners partly because the words are near-homophones for many speakers. "Then" relates to time or sequence — "the government introduced the policy, then reviewed it a year later." "Than" is used for comparisons — "the policy was more effective than expected." A quick check: if you can replace the word with "next" or "at that time" and the sentence still works, it should be "then"; if you're comparing two things, it should be "than."

Lose/loose is a spelling confusion rather than a meaning confusion, but it appears constantly in essays about competition, sport, or economics. "Lose" (one "o," rhymes with "choose") is the verb meaning to be deprived of something or to fail to win: "small businesses risk losing customers to larger competitors." "Loose" (two "o"s, rhymes with "goose") is an adjective meaning not tight or not fixed in place: "loose regulations allowed the practice to continue." These are genuinely unrelated words that happen to be one letter apart, which is precisely why the error is so easy to make without noticing.