甚麼是Gerunds?

GERUND is an –ing form of a verb (verb-ing) that functions as a noun.

Walking is good for you. (~ as subject)
She loves singing. (~ as object)
His worst habit is stealing. (~ as subject complement; not present continuous tense)

Travelling to the desert requires careful preparation.
Travelling to the desert ~ a gerund phrase. It acts as subject.

A gerund phrase is a gerund and its associated modifiers, all of which function as a noun (or nominal).

INFINITIVE is the simplest form of the verb. It is the base form that follows I, you, we and they in the present simple tense. e.g. go (not goes, going, went, gone)

Sometimes the infinitive follows “to”, and we call this the ‘full infinitive” or infinitive with to. ‘to” is called infinitive marker in this case.
He wanted me to go.

Infinitive can be used as a noun, an adjective or an adverbial.
To swim is my greatest love. (~ as subject)
My friend love to ski. (~ as object)
We need clean air to breathe. (~ as adjective)

BARE INFINITIVE is the infinitive of a verb without a preceding “to”. Bare infinitive is thus identical with the base form of the verb. It is used
(1) after the main modal verb.
I must/shall go.
I don’t know.
Do I know you?
(2) verbs of perception e.g. see, hear, feel
I saw/heard him go.
(3) verbs such as make and let
Let him go. (~ also known as infinitive without ‘to’)

The English language only allows us to omit “to” in infinitives placed after certain verbs in the active voice.

小心 usage:
I want to go. (not “I want going”)
Do you mind opening the window? (not “Do you mind to open the window?”)

小心 to 是 infinitive marker 還是 preposition
I want to go.
I am looking forward to seeing you. (to 是 preposition)

題外:
Present participle is another –ing form of a verb. Don’t mix it up with gerund. Together with auxiliary “be”, it makes present progressive aspect. It can be used as adjective. A present participle can head a present participial phrase.

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https://www.youtube.com/watch?v=DS_SDdxQrNc
https://www.youtube.com/watch?v=QuJCaiySNU0

The bare infinitive without --to used after special finites can(could),do(did), may(might), shall(should), will(would), must, need, dare, eg;You must come with us.You needn't go yet.
The Gerund only:---
The gerund is a noun in the form of the present participle of a verb ending in --ing, but whereas the participle is a verbal adjective, the gerund is a verbal noun.
(a)the subject of a sentence,eg:-
Working in this condition is a pleasure.
The reading of the law took place in the Legco's Office.
(b)The complement of a sentence,eg:-
Seeing is believing.
The only thing that interests her is dancing.
To keep the white elephant is keeping.
(c)The object of a sentence,eg:-
She likes dancing.
Your long hair needs cutting.
Have you finished writing?
I remember seeing him in the night.
(d)The object of a preposition,eg:-She is very fond of dancing.
She began by explaining.
I don't like the idea of spending.
Thank you for returning.
She left without saying.
(e)The gerund has some characteristics of a verb:-eg:-
His hobby is collecting stamps.
Meeting you has been a great pleasure.
She left without saying.
I preferred travelling alone !!
She likes driving fast and reading poetry well !!
(f)The gerund takes stress with the hyphen,eg:-
a dancing-teacher(=a teacher of dancing.)
a travelling-rug
a reading- room
a typing- pool
a sleeping-carriage
a running-track.