This looks exactly the same as a present participle, and for this reason it is now common to call both forms ‘the -ing form’. However it is useful to understand the difference between the two. The gerund always has the same function as a noun (although it looks like a verb), so it can be used:
a. as the subject of the sentence:
Eating people is wrong.
Hunting tigers is dangerous.
Flying makes me nervous.
b. as the complement of the verb ‘to be’:
One of his duties is attending meetings.
The hardest thing about learning English is understanding the gerund.
One of life’s pleasures is having breakfast in bed.
c. after prepositions. The gerund must be used when a verb comes after a preposition:
Can you sneeze without opening your mouth?
She is good at painting.
They’re keen on windsurfing.
She avoided him by walking on the opposite side of the road.
We arrived in Madrid after driving all night.
My father decided against postponing his trip to Hungary.
This is also true of certain expressions ending in a preposition, e.g. in spite of, there’s no point in..:
There’s no point in waiting.
In spite of missing the train, we arrived on time.
d. after a number of ‘phrasal verbs’ which are composed of a verb + preposition/adverb
to look forward to, to give up, to be for/against, to take to, to put off, to keep on:
I look forward to hearing from you soon. (at the end of a letter)
When are you going to give up smoking?
She always puts off going to the dentist.
He kept on asking for money.
NOTE: There are some phrasal verbs and other expressions that include the word ‘to’ as a preposition, not as part of a to-infinitive: – to look forward to, to take to, to be accustomed to, to be used to. It is important to recognise that ‘to’ is a preposition in these cases, as it must be followed by a gerund:
We are looking forward to seeing you.
I am used to waiting for buses.
She didn’t really take to studying English.
It is possible to check whether ‘to� is a preposition or part of a to-infinitive: if you can put a noun or the pronoun ‘it’ after it, then it is a preposition and must be followed by a gerund:
I am accustomed to it (the cold).
I am accustomed to being cold.
e. in compound nouns
a driving lesson, a swimming pool, bird-watching, train-spotting
It is clear that the meaning is that of a noun, not of a continuous verb.
the pool is not swimming, it is a pool for swimming in.
f. after the expressions:
can’t help, can’t stand, it’s no use/good, and the adjective worth:
She couldn’t help falling in love with him.
I can’t stand being stuck in traffic jams.
It’s no use/good trying to escape.
It might be worth phoning the station to check the time of the train.