Lexical Resource: precision, not rarity

The criterion most people try to game with a vocabulary list, and the one where that strategy backfires most reliably.

What it measures

Four things, roughly: how wide your vocabulary is, how precisely you use it, whether your collocations are natural, and how much you repeat yourself. Only the first is what candidates study.

Precision is the one that separates bands. A common word used exactly beats an unusual word used approximately, every time, because the unusual word used wrongly is not neutral — it is scored as an error.

The double penalty

This is the part worth understanding, because it changes how you should study.

A rare word used correctly earns you credit under Lexical Resource. A rare word used incorrectly loses you credit under Lexical Resource and appears in the error count that shapes your Grammatical Range and Accuracy band when the misuse is grammatical, such as a wrong preposition or the wrong part of speech.

So the expected value of reaching for a word you are not sure about is negative unless you are genuinely confident. Learning ten words well is worth more than recognising fifty.

Collocation is where non-native writing shows

Collocation is which words habitually go together, and it is largely unpredictable from meaning. Heavy rain and strong wind are both correct; strong rain and heavy wind are both wrong, and no rule explains it.

This is why reading beats memorising. Word lists teach meanings; only exposure teaches which words keep company with which.

Practical version: when you learn a word, learn the phrase around it. Not research, but conduct research. Not decision, but reach a decision.

Repetition

Repeating the same content word in every sentence is penalised, and it is easy to fix badly. Reaching for a thesaurus synonym you do not control is the misuse problem again.

The safer routes are the ones covered under cohesion: refer back with a pronoun, name the thing a second way with a phrase you are sure of, or restructure the sentence so the word is not needed twice.

What to do differently

• Reread your own essay and mark every word that is roughly right. That list is your Lexical Resource band.
• Learn collocations, not words.
• Do not use a word in the exam you have never written before. The exam is not the place to test it.
• Topic vocabulary beats general vocabulary. Knowing the words for education, health, environment and technology carries most IELTS prompts.

One caveat: if you are below band 6, range genuinely is your constraint and more vocabulary is the right investment. The advice above matters most from 6.5 upward, where precision is what is actually holding the band down.