When a verb follows a preposition in English, it takes the -ing form. "I am interested in learning Spanish" is correct; "interested in learn" is not.
The rule covers short prepositions like in, at, of and for, and longer ones like before, after, without, instead of and in spite of. The tricky part is the word to: it is usually part of a to-infinitive, but in look forward to and be used to it is a preposition, so the verb takes -ing.
This page lists the common patterns, explains the to trap, and finishes with 20 drill sentences with a rule under every answer.
The rule
The basic rule
- Preposition + verb = verb + -ing.
- "Good at drawing", "interested in learning", "tired of waiting", "thank you for helping".
- The -ing form is a gerund here: it works like a noun after the preposition.
- Never use the base verb or the to-infinitive after a preposition: "good at draw" and "good at to draw" are both wrong.
Common single-word prepositions
- in: interested in reading, succeed in passing.
- at: good at cooking, bad at remembering names.
- of: afraid of flying, tired of repeating the same thing.
- for: famous for winning, thank you for coming.
- about: excited about starting, worried about failing.
- without: left without saying goodbye.
Two-word prepositions
- instead of: "Let us walk instead of driving."
- in spite of: "She passed in spite of missing classes."
- look forward to: "I look forward to hearing from you."
- be used to and get used to: "I am used to working nights."
- object to: "They object to paying the new tax."
The to trap
- To usually introduces an infinitive: "I want to go."
- In look forward to, be used to and object to, to is a preposition, so the next verb is -ing.
- "I look forward to hearing from you" is correct; "to hear" is a common mistake in emails.
- A useful test: if you can put a noun after to, then to is a preposition and the verb takes -ing.
Before, after and by
- Before and after can be prepositions with -ing: "before leaving", "after eating".
- They can also be conjunctions with a clause: "before I left", "after we ate".
- By + -ing explains how something is done: "You learn by practising."
- On + -ing means as soon as: "On arriving home, she called her mother."
Examples
- She is good at solving problems.At is a preposition, so the verb takes -ing.
- I am interested in learning Japanese.In + -ing is the standard pattern.
- He is afraid of flying.Of takes the gerund.
- Thank you for helping me.For introduces the reason, and the verb becomes -ing.
- We left without saying goodbye.Without + gerund.
- I look forward to hearing from you.To is a preposition here, so hearing is correct.
- She is used to working long hours.Be used to + -ing.
- They objected to paying extra.Object to belongs to the to-preposition group.
- After finishing work, he went for a run.After + gerund when the subject is the same.
- You will improve by reading every day.By + -ing explains the method.
Common mistakes
- Wrong: I am interested in learn French. Right: I am interested in learning French.
- A verb after a preposition takes -ing.
- Wrong: She is good at to cook. Right: She is good at cooking.
- Never use a to-infinitive after a preposition.
- Wrong: I look forward to hear from you. Right: I look forward to hearing from you.
- In look forward to, to is a preposition, so the verb takes -ing.
- Wrong: We left without say goodbye. Right: We left without saying goodbye.
- Without is a preposition and needs the -ing form.
- Wrong: He is used to get up early. Right: He is used to getting up early.
- Be used to takes -ing because to is a preposition in this pattern.
Practice drill
Answer all 20 questions. Each answer is marked at once, and the rule is explained under the question.
She is good at ___ problems.
Show answer and explanation
Answer: A. solving After the preposition at, the verb takes -ing.
I am interested in ___ Japanese.
Show answer and explanation
Answer: B. learning In is a preposition, so the gerund learning follows.
He is afraid of ___ in small spaces.
Show answer and explanation
Answer: C. being Of is a preposition and takes the -ing form.
Thank you for ___ me with the boxes.
Show answer and explanation
Answer: D. helping For is a preposition, so helping is the correct gerund.
We left the party without ___ goodbye.
Show answer and explanation
Answer: A. saying Without is a preposition and needs the -ing form.
I look forward to ___ from you.
Show answer and explanation
Answer: B. hearing In look forward to, to is a preposition, so the verb takes -ing.
She is used to ___ long hours.
Show answer and explanation
Answer: C. working Be used to takes -ing because to is a preposition here.
They objected to ___ the extra fee.
Show answer and explanation
Answer: D. paying Object to keeps to as a preposition, so the gerund follows.
After ___ work, he went for a run.
Show answer and explanation
Answer: A. finishing After as a preposition takes the gerund when the subject matches.
You will improve by ___ every day.
Show answer and explanation
Answer: B. reading By + -ing explains the method.
I am tired of ___ the same question.
Show answer and explanation
Answer: C. answering Tired of takes the gerund answering.
He is famous for ___ fast.
Show answer and explanation
Answer: D. driving For is a preposition, so driving is correct.
She left without ___ a word.
Show answer and explanation
Answer: A. saying Without takes the -ing form saying.
We talked about ___ a new car.
Show answer and explanation
Answer: B. buying About is a preposition and takes the gerund.
On ___ home, she called her mother.
Show answer and explanation
Answer: C. arriving On + -ing means as soon as she arrived.
He apologised for ___ late.
Show answer and explanation
Answer: D. being For is a preposition, so being is the gerund.
She kept the secret without ___ anyone.
Show answer and explanation
Answer: A. telling Without takes the gerund telling.
I am worried about ___ the exam.
Show answer and explanation
Answer: B. failing Worried about takes the -ing form.
Before ___ the house, turn off the lights.
Show answer and explanation
Answer: C. leaving Before as a preposition takes the gerund when the subject is the same.
They succeeded in ___ the race.
Show answer and explanation
Answer: D. finishing Succeed in takes the gerund finishing.
Questions learners ask
Why do verbs take -ing after prepositions?
A preposition needs a noun or a noun-like word after it. The -ing form of a verb works like a noun: "swimming is fun", "I enjoy swimming". So after a preposition, English uses the -ing form: "good at swimming", "interested in learning".
How do I know when to is a preposition?
If you can follow to with a noun, it is a preposition: look forward to your reply, used to the noise, object to the plan. In those phrases, a verb after to takes -ing: look forward to hearing, used to working, object to paying. If to cannot take a noun, it is part of an infinitive: want to go, decide to stay.
What is the difference between "before leaving" and "before I left"?
Both are correct. Before leaving uses the preposition before plus -ing because the subject is the same as the main clause. Before I left uses the conjunction before plus a full clause. Use the -ing form when the subjects match, and the clause when they are different: "Before I left, she called."
More grammar topics
Another vs other vs others
Another adds one more of the same kind, other describes different things, and others stands alone as a pronoun.
Countable and uncountable nouns
The two noun groups, the words that only work with each, the measures that make uncountables countable, and the nouns with two meanings.
Present perfect vs past simple
The classic contrast: finished time takes the past simple, a link to now takes the present perfect.
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