Do collocations actually raise your vocabulary score? Yes — more than rare words

What a collocation is

A collocation is simply which words go together. Not a rule, not a grammar point — a habit that English has and that you have to learn one pair at a time.

Notice that the left column is not ungrammatical. Every one of those phrases obeys the rules of English. They are simply not what anyone says — and that is exactly the thing an examiner hears.

McCarthy and O'Dell open English Collocations in Use by saying it more precisely than we can:

"Not absolutely wrong, but not what a fluent speaker would say" is the whole category. It is also the reason collocation is so easy to ignore: nothing about did a few mistakes breaks a rule you could look up, so it survives every grammar check you run on yourself. It is invisible to you and audible to everyone else.

Their own minimal pair makes the point better than any rule could: fast cars, fast food — but a quick glance, a quick meal. Two adjectives that mean nearly the same thing, and they are not interchangeable. There is no principle underneath that. It is simply what English does, and you learn it one pair at a time.

Strong and open collocations — and why the difference is your whole strategy

The book draws a distinction in its first unit that most collocation study ignores, and it is the one that decides how you should spend your time:

Those two kinds of collocation do completely different jobs for a candidate, and this is where we would push the advice further than the book does.

Why the score rewards it

The IELTS band 7 descriptor for Lexical Resource asks for some awareness of style and collocation. It is named. It is not a hidden criterion or a matter of taste.

And the descriptors penalise inappropriate and inaccurate word choice, which is exactly what a collocation error is: the right meaning, the wrong partner.

Why the thesaurus does the opposite

The usual advice — do not repeat words, use synonyms — sends candidates to a thesaurus, and a thesaurus does not know about collocation. It gives you words that share a meaning, not words that share a partner.

So the synonym strategy produces the exact error the criterion punishes, while feeling like sophistication. The collocation strategy produces the exact quality it rewards, while feeling like plain English. That is the whole trade.

How to study them so they stick

McCarthy and O'Dell devote their second unit to exactly this, and their method is three steps: find, record, learn. It is worth following closely, because each step contains a correction to what most learners actually do.

1. Record the pair inside a phrase, never the word alone. Their instruction is to write down a collocation "in a phrase or a sentence showing how it is used" — I don't have access to that kind of information, not access. The unit that scores is the pair in use, so that is the unit to store.
2. Group them — by topic, and also by the shared word. This is the step people skip. Take one ordinary word and collect its family: find a way, find your way back, learn the hard way, get in your way, give way to traffic, try every possible way. Six collocations, one word you have known for years.
3. Find them by noticing, not by downloading a list. Their first instruction is to train yourself to notice collocations whenever you read or listen to English. The pairings that surprise you are the ones your instincts get wrong, which makes them precisely the ones worth writing down.
4. Practise them in contexts that are meaningful to you personally. Their words, and the reason lists fail: a collocation you have only read is not learned. Put five into a spoken answer or an essay within a day of meeting them.

The grouping step is the one we would underline hardest. A candidate who learns twenty rare words has twenty words. A candidate who takes way, make, take and give and collects everything each of them pairs with has a hundred natural phrases, built from four words they already own.

For the test, and for real English

For the test: collocation is named in the band 7 descriptor, it fixes repetition without a thesaurus, and it raises your score with vocabulary you already have. Hour for hour it is the best vocabulary investment available to you.

For real English: this is the rare case where the exam is pushing you in exactly the direction real fluency goes. Collocations are what make you sound natural to a colleague, a friend, a stranger — for the rest of your life. Unlike a list of exam idioms, you will use these every single day.

So this is not a test technique that you throw away afterwards. It is simply how you learn English properly, and the exam happens to reward it. Take the alignment where you find it.

One place the two rooms genuinely come apart — and the book says so first

McCarthy and O'Dell list three reasons to learn collocations: they give you the most natural way to say something, they give you more precise or expressive alternatives, and they improve your style in writing — poverty breeds crime rather than poverty causes crime, a substantial meal rather than a big meal. And then they add a qualification that is easy to read past:

The authors are drawing the same line we do. Some collocations are written collocations. Poverty breeds crime is excellent in an essay and slightly odd said aloud over coffee, and knowing which is which is itself part of what the descriptors call awareness of style.