IELTS grammar: Gerunds vs. Infinitives

Gerunds and infinitives cause a distinctive kind of error in IELTS Writing and Speaking, because unlike most grammar points on this list, there is no underlying logical rule a candidate can reason through in the moment — whether a given verb takes a gerund, an infinitive, or either, is essentially a memorised fact about that specific verb, inherited from centuries of English usage rather than derived from any consistent pattern. This means the error pattern looks different from most other grammar mistakes: candidates who are otherwise strong tend to get common, frequently-practised verbs right (enjoy, want, decide) but slip on less common verbs they haven't specifically drilled, and the error appears essentially at random from an outside observer's perspective, which is exactly why examiners read it charitably compared to more systematic tense or article errors — but it is still worth minimising, since a handful of these errors scattered through an essay still counts against range and accuracy.

A gerund is the -ing form of a verb functioning as a noun: "Swimming is good exercise," "I enjoy reading in the evenings." An infinitive is "to" plus the base verb: "I want to swim," "She decided to leave early." Some verbs are followed only by a gerund, some only by an infinitive, and some by either, sometimes with identical meaning and sometimes with a meaningful difference — and there is no shortcut to knowing which category a given verb falls into beyond learning it directly.

Common gerund-only verbs include "enjoy," "avoid," "consider," "suggest," "finish," "mind," "practise," "risk," and "admit." INCORRECT: "I enjoy to read in the evenings." CORRECT: "I enjoy reading in the evenings." INCORRECT: "The report suggests to invest in renewable energy." CORRECT: "The report suggests investing in renewable energy." Common infinitive-only verbs include "want," "decide," "plan," "hope," "agree," "afford," "manage," "promise," and "refuse." INCORRECT: "I decided leaving the company." CORRECT: "I decided to leave the company." These two lists are worth memorising as fixed sets, since no amount of grammatical reasoning about the sentence's structure will correctly predict which category a new verb belongs to.

Some verbs take either form with essentially no change in meaning, where either choice is acceptable: "start," "begin," "continue," and "like" (in British English particularly, "like" is comfortable with both — "I like swimming" and "I like to swim" are both correct, with a subtle difference some grammarians describe as general enjoyment versus a considered choice, though in practice this distinction is faint enough that either is safe to use). This flexible category is useful to know precisely because it means a candidate uncertain about a specific verb can sometimes sidestep the uncertainty by choosing a different, more familiar verb from this flexible group instead.

The genuinely tricky sub-category, and the one worth specific attention, is verbs that change meaning depending on which form follows. "I stopped smoking" means the smoking habit itself ended — the gerund describes the activity that was stopped. "I stopped to smoke" means a different activity was paused in order to smoke — the infinitive here describes the purpose of stopping, not the thing being stopped. These are both fully grammatical sentences with entirely different real-world meanings, so this is not a minor style issue; getting it wrong can genuinely confuse a reader or listener about what actually happened. Similarly, "I remember locking the door" (a memory of the past action of locking it) differs from "I remembered to lock the door" (successfully performing a required future action, then recalling that it needed doing) — "remember + gerund" looks back at a completed memory, while "remember + infinitive" looks forward to a task that needed doing and was (or wasn't) done.