IELTS Writing Synonyms: When Swapping a Word Costs You a Band

A synonym list tells you what you may swap. It does not tell you when swapping is the wrong move, and that is the part that decides your Lexical Resource band.

This page starts from what the criterion asks for, shows the one place in the Writing paper where you genuinely need a synonym, and then repairs three real sentences from an answer in our library where the swapped words were named in the feedback as the thing holding the band down. The bands quoted here are estimates from Bandly's scoring engine, not marks from a qualified examiner.

What the Lexical Resource criterion actually rewards

Read the public band descriptors for Lexical Resource from band 5 upwards and notice which words repeat. At band 6 the range is adequate and there are noticeable errors. At band 7 there is a sufficient range with some awareness of style and collocation, and some less common items. At band 8 vocabulary is used fluently and flexibly to convey precise meanings. At band 9 it is wholly natural.

Three things are being measured there: range, precision and naturalness. Only one of them, range, is helped by knowing more words. The other two can be damaged by using them.

That is the whole problem with the synonym list as a study method. A list hands you range and leaves you to supply precision and naturalness yourself, in a language you are still learning, under exam time pressure. A word you half know, placed in a sentence you wrote quickly, is a word choice error, and word choice errors are what the band 6 and band 7 descriptors are explicitly about.

The one place a synonym is genuinely required

Both tasks print a prompt, and you have to restate it. Copying the prompt sentence word for word gives the marker nothing to assess, because copied text is not your language. So the opening sentence of a Task 1 answer or a Task 2 essay does need you to say the same thing in different words.

That is paraphrasing, not synonym substitution, and the difference is the unit you change. A paraphrase restructures the sentence: it changes the grammar, the order and the noun phrases together, so the result sounds like something a person would write. Synonym substitution keeps the structure and swaps single words, which is how you end up with sentences that are grammatically fine and read as though a dictionary wrote them.

Our post on paraphrasing the question works through that restructuring in detail. For the rest of your answer, the original word is usually the right word, and repeating a key noun is normal in English writing. Nobody loses marks for using transport three times in a transport question.

A real sentence, repaired

Here is the opening of a Task 1 Academic answer published in our sample library. It was estimated at 7.5 overall, with Task Achievement at 9 and Lexical Resource at 7.

The bar chart illustrates the proportion of commuters utilizing four modes of transportation, namely train, bus, car, and bicycle, across three distinct cities of Tokyo, Amsterdam, and Houston in the year 2023.

Nothing here is wrong. It is also carrying four substitutions that cost more than they bought, and the feedback on this answer named two of them directly, saying that replacing repetitive structures like accounting for and utilized by with more varied language was what stood between this criterion and a higher band.

The repair, with the structure changed rather than the words alone:

The bar chart shows how commuters in Tokyo, Amsterdam and Houston travelled to work in 2023, comparing four types of transport: train, bus, car and bicycle.

That version is shorter, says the same thing, and reads naturally. It addresses Lexical Resource through precision, since travelled to work is what commuting means, and it addresses Coherence and Cohesion, because the sentence now groups the cities and the transport types instead of threading them through one long chain.

Two more from the body of the same answer:

1. "the train was by far the most popular mode of transport, accounting for 62% of all commuters" becomes "the train was by far the most popular choice, used by 62% of commuters". Accounting for is correct with a share or a percentage, but the phrase appears three times in this short answer, twice as accounting for and once as accounted for, which is the repetition the feedback named. Changing the second and third instances is a Coherence and Cohesion repair as much as a vocabulary one.
2. "car transport was overwhelmingly dominant, utilized by 88% of commuters" becomes "88% of commuters drove". The original uses nine words and a passive to say what three words say. Precision at band 8 is described as conveying precise meanings fluently and flexibly, and that is what shorter, more direct writing demonstrates.

Notice that none of these repairs added a longer word. Every one of them removed one.

Task 1 trend language: which swaps are real

Task 1 is where synonym lists are most useful, because the data genuinely does the same few things. Even here, the words are not interchangeable.

The pattern is that the safe variations are ordinary words of the same strength, and the risky ones are stronger words that smuggle in a claim about the size of the change. A chart does not care how excited you are. Our post on vocabulary where precision beats length has more on that trade, and collocation and the Lexical Resource band covers which words naturally go together, which is the part a synonym list cannot give you.

The three ways a synonym actually loses marks

Register. Writing is a formal register in both tasks. Kids for children, youngsters for young people, stuff for things and a lot of for many read as speech. A letter to a friend in General Training is the one place informal choices are right, and even there they must be consistent.

Collocation. Words have company they keep. You make a decision and take a step; do a decision is not wrong vocabulary, it is wrong pairing, and collocation is named in the band 7 descriptor. Lists of single words tell you nothing about this.

Word formation. The commonest error of all, and the one that pulls the criterion furthest down. Informations for information, peoples for people, develope for develop. These three all appear in answers published in our library, and in each case the swapped-in word was not harder than the original, it was simply the wrong form of a word the writer already knew.

What the library's lexical notes show

We read the Lexical Resource note recorded for all 25 published samples in Bandly's library. Every one of them names word choice, word formation or spelling as the thing limiting that criterion. The band spread is the useful part: 3 at band 5, 14 at band 6, 6 at band 7 and 2 at band 8.

One caution. The engine writes these notes from a standard set of phrasings for each criterion, so the uniformity is partly the engine's style, not a measurement, and these bands have never been compared against a qualified examiner's marks. What the spread does show is that 17 of 25 answers sat at band 6 or below on vocabulary while none of them was short of words. They were short of accuracy.

You can read whole answers with their criterion notes attached on the band 6 samples hub, which collects the estimates in that range, and the Academic Task 1 hub holds the answer repaired above.

What to do today

Take your last answer and do the opposite of what a synonym list asks. Go through it and replace every word you chose to sound impressive with the plainest word that says the same thing. Then read the result aloud. If it sounds like a person explaining something, you have gained precision and lost nothing a marker rewards.

Then pick the five words you actually need for your topic area, check each one in a dictionary for the words it normally appears with, and learn those pairs rather than ten more alternatives. When you want to see which of the four criteria your vocabulary choices are holding back, paste the answer into Bandly for a separate estimate of each one.