WHAT IS A GERUND?
A gerund is a word ending in (ing) that is made from a verb and used as a noun.
Sometimes students confuse gerunds with present continuous verbs. Look at the word reading in the following two sentences.
Verb (present continuous) I am reading right now.
Gerund (noun) I enjoy reading before I go to sleep.
WHY DO WE NEED GERUNDS?
Gerunds are flexible words which allow us to talk about an action as a noun.
The word dancing in the next sentence is not a verb, it is the name of the activity Marco loves to do. Marco loves dancing. Is Marco dancing now? No.
Because nouns are more flexible than verbs, gerunds allow us to use action words (verbs) as the subject, the complement, or the object of a sentence.
Subject Dancing makes Marco happy.
Complement Marco's favourite hobby is dancing.
Object Marco loves dancing.
WHAT IS AN INFINITIVE?
An infinitive is the verb form that has (to) at the beginning. For example, (to sing).
Infinitives can also be used as the subject, the complement, or the object of a sentence.
Subject To sing is her joy.
Complement The most important thing is to sing.
Object She wants to sing.
Whether to use a gerund or an infinitive depends on the main verb in the sentence.
The gerund is more common as the subject or the complement and sounds better most of the time. Using an infinitive as the subject sounds more philosophical.
To be or not to be
It is more difficult to decide between a gerund and an infinitive for the object of the sentence. Usually, the main verb in the sentence helps you make the choice.
After certain verbs including fancy, enjoy, love, like, fancy, dislike, mind, recommend, suggest, keep, avoid, finish.
After prepositions of place and time.
I made dinner after getting home.
She looked scared before seeing her exam results.
To replace the subject or object of a sentence
Swimming is a popular sport in my country.
Maher likes eating pizza.
Can be used after certain verbs including agree, ask, decide, help, plan, hope, learn, want, would like, and promise.
After many adjectives
It is hard to make dinner on my own.
I find it difficult to describe my feelings about Australia.
To show purpose
I came to Australia to learn English.
I went back to Japan to save money.