Short answer: IELTS sentence completion comes in two variants — completing a sentence with words copied from the passage under a strict word limit, and matching the start of a sentence to its correct ending from a list. Both follow the order of the passage.
The marks are won by predicting the grammar of each gap, respecting the word limit to the letter, and locating the answer through paraphrase rather than matching words.
Sentence completion looks straightforward next to the intimidating multiple-answer and matching tasks, and that is precisely why candidates leak easy marks on it.
The information you need is usually easy to find and easy to understand — the losses come from mechanical failures: exceeding the word limit by one article, writing the right idea in the wrong word form, or choosing a sentence ending that fits the grammar but contradicts the passage.
This guide covers the two variants, word-limit discipline, grammar prediction, locating via paraphrase, the specific strategy for matching sentence endings, a worked example, and the common errors that turn should-be marks into zeros.
The two variants
The first variant, sentence completion, gives you incomplete sentences and asks you to fill each gap with words taken directly from the passage, subject to a stated word limit such as NO MORE THAN TWO WORDS.
The answer must appear in the text exactly as you write it — your job is to locate it and copy it precisely.
The second variant, matching sentence endings, gives you a set of sentence beginnings and a longer list of possible endings, and you choose the ending that completes each sentence accurately according to the passage. There are always more endings than beginnings, so several endings are never used.
| Feature | Sentence completion | Matching sentence endings |
|---|---|---|
| What you write | Words copied exactly from the passage | The letter of the correct ending |
| Word limit | Yes — stated in capitals and strictly enforced | No — you choose from a list |
| Spelling risk | Yes — a misspelt answer is marked wrong | None |
| Follows passage order? | Yes | Yes (by the beginnings) |
| Main difficulty | Word form and obeying the limit | Endings that fit grammatically but not in meaning |
Diagnose which variant you face before doing anything else — the presence of a word limit and the absence of an endings list tell you instantly.
The two are close relatives of the summary tasks; if you have worked through our summary completion tips, the from-the-passage half of sentence completion will already feel familiar, because the underlying discipline — predict grammar, locate via paraphrase, copy exactly — is identical.
Word-limit discipline
The instruction "NO MORE THAN TWO WORDS AND/OR A NUMBER" is a contract, and IELTS enforces it without mercy: exceed the limit and the answer is wrong even when the meaning is perfect. So learn the counting rules cold.
A hyphenated word counts as one word, so well-being is a single word. A number written in figures counts as a number, not a word — writing 25 uses none of your word allowance, while writing twenty-five spends a word.
Articles count: the water cycle is three words and fails a two-word limit, even though water cycle alone would be correct.
The practical rule that follows is simple: never add words the gap does not need. If the sentence around the gap already supplies the article or an adjective, do not import another word from the passage out of caution — extra words add risk and never add marks.
And because these are Reading answers copied from the text, spelling counts too. IELTS accepts standard alternative spellings, including British and American variants such as colour and color, but it does not accept invented ones, so copy the word exactly as the passage spells it.
Make word-counting a physical ritual in practice — touch a finger for each word before you move on — until checking the limit is automatic.
Predict the grammar of the gap
The highest-value habit in this task takes under a minute and pays off in both variants: read each gapped sentence first and decide what part of speech the gap needs. After a, an, the or an adjective, the gap wants a noun.
Between a subject and an object, it wants a verb, and the surrounding tense tells you which form. Before a noun, it likely wants an adjective. If the verb beside the gap is are rather than is, the noun you need is plural.
Jot n., v. or adj. beside each gap; the notation costs seconds.
In sentence completion the payoff is that you stop grabbing the thematically-right, grammatically-wrong word that so often sits one sentence away from the real answer.
In matching sentence endings the payoff is a fast filter: an ending has to make a grammatical sentence with the beginning, so any ending that produces a broken sentence can be eliminated before you even weigh its meaning.
Grammar prediction is the same reflex that carries you through the summary tasks and the box-elimination variants across the Reading paper.
Locate via paraphrase
Both variants follow the order of the passage — the answers, or the sentence beginnings, appear top to bottom — so once you have found where answer one lives, answer two is below it. Use that to keep your search moving forward rather than re-reading.
But locating the right sentence still means seeing through paraphrase, because the gapped sentence is a reworded version of the passage, not a quotation of it. "Scientists eventually discovered" in the passage may appear as "the eventual discovery" in the question; "people who took part" may become "participants".
Here is the reassuring asymmetry of the from-the-passage variant: everything around the gap is paraphrased except your answer. You decode the rewording to find the right sentence in the passage, and then you stop translating and copy the exact word the passage uses.
You paraphrase your way to the location, then lift the answer verbatim.
Training that decoding reflex is a study project of its own — our guide on how to improve IELTS Reading builds it, and reading well-edited English regularly, such as the free materials in the Cambridge English learning resources, develops the same instinct passively.
Matching sentence endings strategy
Matching sentence endings behaves differently enough to need its own routine. The sentence beginnings follow the passage order, so work them top to bottom, and for each beginning locate the relevant sentence in the passage first — before you look at the endings list.
Read the passage's version of the idea, form your own sense of how the sentence should finish, and only then scan the endings for the one that matches your prediction.
Coming to the list with an expectation is far safer than reading all the endings cold and picking the one that "sounds right".
Apply two filters in order. First, grammar: read the beginning joined to each candidate ending and discard any that do not form a grammatical sentence — subject-verb agreement, tense and singular/plural often eliminate several at once.
Second, meaning against the passage: of the endings that fit grammatically, only one will be true according to the text.
The others are the task's signature trap — endings that are grammatically perfect and often factually true somewhere in the passage, but not the true completion of this beginning.
Never choose an ending because it states something the passage says; choose it because it accurately completes the specific sentence you are working on.
A worked example
The passage and questions below were written for this article as teaching examples, in the style of a test paper. First, sentence completion.
Passage: "The lighthouse was built from local granite, chosen because the stone could withstand the constant battering of the waves. Its lamp, originally fuelled by oil, was automated in 1998, and the last keeper left the following year."
Question (ONE WORD ONLY): "The lighthouse's lamp was originally powered by ______." Predict the grammar: after "powered by" the gap wants a noun.
Decode the paraphrase: "the lamp was originally powered by" maps onto "Its lamp, originally fuelled by oil" — "powered by" is simply a reworded "fuelled by", and "originally" is repeated to point you at the same clause.
The noun that fills the gap is therefore oil: one word, copied exactly as the passage spells it.
A candidate who reasons that the lamp was later "automated" and writes "electricity" scores nothing — that is inference, not the word the text supplies, and the answer must be lifted verbatim from the passage.
Now matching sentence endings, from a different passage: "Bamboo grows faster than almost any other plant, some species extending by nearly a metre in a single day. Because its roots knit the soil together, it is increasingly planted on slopes to prevent landslides. Manufacturers value it too: harvested stems can be processed into flooring that rivals hardwood for durability."
Beginning: "Bamboo is planted on hillsides because…" Endings: A. …it can grow almost a metre in one day. B. …its roots hold the soil in place. C. …it is as durable as hardwood. D. …it is cheaper than other materials. All four are grammatical, so grammar cannot decide.
Meaning does: the passage says bamboo is "planted on slopes to prevent landslides" because "its roots knit the soil together", which paraphrases to B, its roots hold the soil in place.
Ending A is true (the growth-speed fact) but answers a different beginning; ending C is true (the flooring durability) but irrelevant to why it is planted on slopes; ending D is never stated.
The answer is B — the only ending that both fits and is true for this sentence.
Common errors
Four errors account for most lost marks. Right meaning, wrong word form: the gap needs a noun and you copy a verb from the passage — understood everything, scored nothing.
In the from-the-passage variant you cannot adapt the form, so if it does not fit, you are in the wrong place; keep searching.
Over-copying past the limit: the passage offers a long phrase and the anxious candidate copies it whole; the extra word converts a correct answer into a wrong one.
Choosing an ending by grammar alone: several endings fit grammatically, and picking the first that reads smoothly ignores the meaning-check that actually decides.
Ignoring passage order: forgetting that answers run top to bottom and re-scanning the whole text for each gap, burning time you do not have.
Every one of these is a discipline failure rather than a knowledge gap, which is good news — disciplines are trainable. The same "plausible but wrong" engineering behind the grammatical-but-untrue ending appears across the paper, and our guide to IELTS Reading traps maps the whole family so you learn to expect it.
Conclusion
Sentence completion and matching sentence endings are among the most winnable tasks on the Reading paper, precisely because their difficulty is mechanical rather than conceptual. Identify the variant first.
In sentence completion, predict the grammar of each gap, obey the word limit to the letter, and copy the answer exactly as the passage spells it — locating it through paraphrase but never rewording it.
In matching sentence endings, find the passage's version of each beginning first, filter the endings by grammar, then let meaning against the text pick the survivor.
Trust the passage order to keep your search moving forward, and drill each variant by type until the four common errors — wrong form, over-copy, grammar-only choice, and lost place — stop happening.
Get the discipline right and these tasks become a dependable source of marks rather than a quiet drain on them.