Short answer: a collocation is a word pairing that native speakers use by convention — "heavy traffic", not "strong traffic". Collocation accuracy is the single biggest Lexical Resource difference between band 6 and band 7, because the error is invisible to the writer: every individual word is correct and the sentence still reads wrongly.
This is why collocation is worth more of your study time than new vocabulary. You already know "make", "do", "traffic" and "research". What costs you the band is pairing them the way your first language pairs them.
Why collocation, not vocabulary size, is the band 7 gate
At band 6 the descriptors note vocabulary that is adequate but shows inaccuracies in word choice and collocation. At band 7 the requirement is vocabulary used with "some flexibility and precision", with only occasional errors.
The gap between the two is almost never the number of words a candidate knows — it is whether the words they know sit in their natural company.
Collocation errors also compound: a single wrong pairing in a topic sentence weakens the whole paragraph, because the examiner has been told what the paragraph is about in slightly wrong English.
The pairings that fail most often
| What candidates write | The natural pairing | Why the wrong one is tempting |
|---|---|---|
| make a research | conduct / carry out research | Research is uncountable, and "make" is the default verb in many first languages. |
| do a mistake | make a mistake | Make/do is arbitrary in English and systematic in most other languages. |
| strong traffic | heavy traffic | "Strong" collocates with wind, coffee and evidence — not traffic. |
| take a decision | make a decision | "Take a decision" exists in British formal usage but is risky; "make" is always safe. |
| high crime | a high crime rate | The measurable noun is missing. Crime itself is not high or low. |
| solve a problem of pollution | tackle / address pollution | "Solve" promises a complete solution, which over-claims in Task 2. |
| gain knowledge about | acquire knowledge of | The preposition is part of the collocation and is marked lexically. |
| big improvement in salary | a substantial pay rise | Register: "salary improvement" is technically parseable but unnatural. |
| discuss about | discuss | Discuss is already transitive. The added preposition is a lexical error. |
| pay attention on | pay attention to | Preposition pairing, learned as a unit or not at all. |
By topic — because that is how you will need to retrieve them
Education
- pursue higher education · attend a lecture · sit an examination · meet a deadline
- acquire a skill · broaden your horizons · a rigorous curriculum · vocational training
- bridge the skills gap · a heavy workload · academic achievement · drop out of school
Error to avoid: "make a degree" and "pass a lecture". You take or do a degree and attend a lecture.
Environment
- reduce carbon emissions · adopt renewable energy · conserve natural resources
- a fragile ecosystem · pose a threat to · irreversible damage · offset emissions
- impose stricter regulations · raise public awareness · a sustainable alternative
Error to avoid: "destroy the environment badly". Use "cause irreversible damage to the environment" — the adverb is doing work the verb should do.
Technology and work
- automate routine tasks · disrupt an industry · adopt new technology · bridge the digital divide
- a demanding role · a competitive salary · career progression · work remotely
- boost productivity · streamline a process · retrain the workforce · job security
Error to avoid: "make a job" and "win a salary". You get or secure a job and earn a salary.
Health
- lead a sedentary lifestyle · a balanced diet · alleviate symptoms · a chronic condition
- place a strain on healthcare systems · preventable illness · life expectancy
- seek medical attention · adhere to treatment · a public health campaign
Error to avoid: "make sport". You do sport, play a named team game and go swimming.
Government and society
- implement a policy · allocate funding · impose a ban · enforce a regulation
- address inequality · widen the gap between · a pressing social issue
- place a burden on taxpayers · public expenditure · social cohesion
Error to avoid: "the government should make a law". Governments pass, introduce or enact legislation.
Task 1 data language
- a marked increase · a steady decline · fluctuate wildly · plateau at around
- peak at · account for a quarter of · a downward trend · remain stable
- outstrip · overtake · a negligible proportion · more than double
Error to avoid: "increase dramatically" for a two-percent change. Strength must match the data, and over-claiming is charged to Task Achievement as well as to vocabulary.
How to learn a collocation so it holds
- Record the whole chunk. "Conduct research into", never "conduct" alone. The preposition is part of it.
- Group by topic, not alphabetically. Under exam pressure you retrieve by subject, so store by subject.
- Write one true sentence with each. A collocation you have used once is retrievable; one you have read ten times is not.
- Check pairings you are unsure of, do not guess. A guessed pairing is the exact error this page is about, and it is invisible to you.
- Keep a personal error list. Your collocation errors come from your first language and will repeat. Five of them probably account for most of your losses.
Collocation is also the reason a band score for Lexical Resource on its own is more useful than an overall score — it tells you whether this is your limiting criterion or not.
The Writing Checker reports each criterion separately, and Word Coach delivers each new word with its collocations rather than as a bare definition.
For the replacement side of the same problem — which basic words to upgrade and how each upgrade backfires — see the synonym upgrade table.