Lexical Resource (vocabulary) is one of the four IELTS Writing assessment criteria, and it is often the criterion where candidates lose the most points due to specific, correctable errors. Many candidates use impressive-sounding vocabulary but make collocation errors, word formation mistakes, or register mismatches that signal limited vocabulary control to examiners. This guide covers the most impactful vocabulary mistakes.
1Collocation Errors: The Hidden Vocabulary Problem
Collocation errors are the most significant vocabulary mistake in IELTS Writing — and the hardest to self-identify, because the word choice may seem logical. Collocations are fixed phrases where specific words must appear together. Examples of collocation errors: 'make damage' (correct: 'cause damage'), 'do a mistake' (correct: 'make a mistake'), 'strong poverty' (correct: 'severe poverty'), 'highly improve' (correct: 'greatly improve' or 'improve significantly'), 'increase the awareness' without article is informal — 'raise awareness' is the standard collocation. Fix: when learning new vocabulary, always learn the full collocation, not just the word. Never look up a word and memorise it alone — find it in a sentence and memorise the phrase. Collins COBUILD Collocations Dictionary is an excellent reference.
2Word Formation Errors
Word formation errors — using the wrong part of speech — are very common in IELTS Writing at Band 5–6. Examples: 'The environment has become worse due to the pollute of factories.' (Correct: 'pollution') 'The government needs to education people about this issue.' (Correct: 'educate') 'This problem is very significance.' (Correct: 'significant') Fix: know the four forms of each key academic word. For 'significance': noun: significance / verb: signify / adjective: significant / adverb: significantly. Study word families for the 100 most common AWL words — this systematically prevents word formation errors.
3Register Errors: Too Informal for Academic Writing
IELTS Academic Writing requires a formal, academic register. Register errors — using informal language in a formal context — are extremely common. Common informal words and their formal alternatives: 'kids' → 'children', 'a lot of' → 'a significant number of / numerous', 'get' (in most senses) → 'receive', 'obtain', 'become', 'big' → 'substantial', 'considerable', 'bad' → 'detrimental', 'harmful', 'negative', 'good' → 'beneficial', 'advantageous', 'positive', 'show' → 'demonstrate', 'illustrate', 'indicate'. Contraction errors: contractions ('don't', 'it's', 'can't') are not appropriate in Academic Writing. Always use full forms. Fix: keep a list of informal words you habitually use and their formal equivalents. Review this list before every practice essay.
4Over-Using Sophisticated Words
A counterintuitive vocabulary mistake: over-using rare or sophisticated words to demonstrate vocabulary range, when they are not actually the most appropriate choice. Examiners can identify when vocabulary is being forced for effect rather than used naturally. Example: 'The perspicacious student unequivocally elucidated the paramount difficulties inherent in the contemporary educational paradigm.' This sentence prioritises sounding impressive over communicating clearly — and the vocabulary choices include some that are wrong for the academic register of IELTS. Band 9 vocabulary is precise and appropriate, not maximum complexity for its own sake. Fix: for each sentence, choose the most precise word for the meaning — not the most impressive-sounding. Natural sophistication outperforms forced complexity in Lexical Resource assessment.
🎯 Key Takeaway
Vocabulary improvement for IELTS is most effective when it targets collocation learning (not isolated word memorisation), word family study (knowing noun/verb/adjective/adverb forms), and register appropriateness (formal language in writing). These three areas cover the majority of Lexical Resource errors at Band 6.