What is the difference between a gerund and an infinitive?

A gerund is the -ing form of a verb used as a noun (swimming, reading). An infinitive is to plus the base verb (to swim, to read). Both let a verb act like a noun, but English verbs are fussy about which one can follow them: enjoy takes the gerund (I enjoy swimming), while want takes the infinitive (I want to swim).

How do I know whether to use a gerund or an infinitive?

It usually depends on the first verb. Some verbs are always followed by the gerund (enjoy, avoid, finish), some are always followed by the infinitive (want, decide, hope), and a few take either. There is no rule that predicts the group, so the most reliable method is to learn the common verbs in lists.

Why is it I look forward to meeting you and not to meet you?

Here to is a preposition, not part of an infinitive. A preposition is always followed by the gerund, so it is look forward to meeting, interested in learning and good at swimming. This is one of the most common errors, because the to looks like an infinitive.

Does the meaning change with stop, remember and try?

Yes. Stop doing means quit; stop to do means pause in order to do something else. Remember doing means recall a memory; remember to do means not forget a task. Try doing means experiment; try to do means make an effort. The form changes the meaning completely.

Gerund and infinitive: which verb form comes next?

When one verb is followed by another, English makes you choose between two forms: the gerund (swimming) and the infinitive (to swim). Get the choice wrong and the sentence sounds off to every native speaker, even though the meaning is usually clear. The hard part is that the rule is not really a rule. It depends on the first verb, and you mostly have to learn which verb wants which form.

What a gerund and an infinitive actually are

A gerund is the -ing form of a verb used as a noun.

Swimming is good exercise. (subject)
I enjoy reading. (object)

An infinitive is to plus the base verb.

I want to leave.
Her plan is to win.

Both turn a verb into something that can sit where a noun sits. The trouble starts when a gerund or infinitive follows another verb, because most verbs accept only one of the two.

Verbs followed by the gerund

These verbs are followed by the -ing form. I enjoy to read is wrong; it has to be I enjoy reading.

Verb	Example
enjoy	I enjoy cooking.
avoid	He avoids talking about it.
finish	She finished eating.
mind	Do you mind waiting?
suggest	They suggested going by train.
can't help	I can't help laughing.
keep	He keeps interrupting.
practise	I practise speaking every day.
miss	She misses living by the sea.
give up	He gave up smoking.

A quick test: many of these describe stopping, continuing or feeling about an activity, but the safest approach is simply to know the list.

Verbs followed by the infinitive

These verbs are followed by to plus the base verb. I want going is wrong; it has to be I want to go.

Verb	Example
want	I want to leave.
decide	We decided to stay.
hope	She hopes to pass.
plan	They plan to move.
agree	He agreed to help.
offer	She offered to drive.
promise	I promise to call.
refuse	He refused to answer.
learn	I learned to swim.
manage	We managed to finish.
would like	I would like to know.

Verbs that take both with no real change

A handful of verbs accept either form, and the meaning stays the same. These are mostly verbs of starting, continuing and liking.

Verb	Both forms work
begin	It began to rain. / It began raining.
start	She started to cry. / She started crying.
continue	He continued to talk. / He continued talking.
like	I like to cook. / I like cooking.
love	They love to travel. / They love travelling.
hate	I hate to wait. / I hate waiting.
prefer	She prefers to walk. / She prefers walking.

There is a faint difference with like: I like to cook can suggest a habit you choose (you cook because it is sensible), while I like cooking is purely about enjoyment. In everyday speech most people treat them as the same.

Verbs that take both, but the meaning changes

This is the group that matters most, because choosing the wrong form changes what you are saying. Learn these properly.

Verb	+ gerund	+ infinitive
stop	quit the activity: He stopped smoking.	pause in order to: He stopped to smoke.
remember	recall a memory: I remember locking the door.	not forget a task: Remember to lock the door.
forget	(rare) recall: I'll never forget meeting her.	fail to do: I forgot to call him.
try	experiment: Try adding salt.	make an effort: I tried to lift it.
regret	be sorry about the past: I regret saying that.	be sorry to announce: We regret to inform you.
go on	continue the same thing: He went on talking.	move to a new thing: She went on to become a doctor.
mean	involve: This job means working late.	intend: I meant to tell you.

Read the stop and remember rows twice. He stopped smoking means he gave it up. He stopped to smoke means he interrupted what he was doing in order to have a cigarette. I remember locking the door is a memory of the act; remember to lock the door is an instruction for later.

The gerund always follows a preposition

This rule is reliable, which is rare in this topic. After any preposition (at, in, of, about, for, before, after, on) you use the gerund, never the infinitive.

She is good at swimming.
I am interested in learning Spanish.
Think before speaking.
He left without saying goodbye.

The trap is fixed phrases that end in to, where to is a preposition rather than part of an infinitive:

I look forward to meeting you. (not to meet)
I am used to working nights. (not to work)
She is committed to helping.

If you can replace the phrase with a noun (I look forward to the holiday), the to is a preposition and needs the gerund.

The bare infinitive (no 'to')

After modal verbs (can, must, should, will, might) and after make and let, you use the base verb with no to at all. This is the bare infinitive.

You must go. (not must to go)
I can swim.
She made me wait. (not made me to wait)
Let him try.

Common mistakes

Ranked by how often learners make them.

Infinitive after a gerund verb. I enjoy to read. Enjoy takes the gerund: I enjoy reading. The same trap hits avoid, finish, mind and suggest.
Gerund after an infinitive verb. I want going home. Want takes the infinitive: I want to go home.
Infinitive after a preposition. I look forward to meet you. The to is a preposition, so use the gerund: I look forward to meeting you.
Wrong form changing the meaning. Stop to smoke when you mean stop smoking tells people the opposite of what you intend.
Keeping the to after a modal. I must to leave. Modals take the bare infinitive: I must leave.

Practice

Choose the correct form. Answers are below.

I enjoy ___ (cook) at the weekend.
She decided ___ (stay) at home.
He is good at ___ (draw).
Remember ___ (post) the letter on your way out.
They must ___ (leave) before nine.

Answers: 1. cooking (enjoy takes the gerund) 2. to stay (decide takes the infinitive) 3. drawing (after the preposition at) 4. to post (a task you must not forget, so the infinitive) 5. leave (bare infinitive after the modal must)