Consider the following sentence.
Reading is a good habit.
Let's find out Subject of this sentence. We have seen that to find the subject of a sentence just ask yourself a question "Who/What + Verb ?". In this sentence you can see that we have two verbs, reading and is. So what will be our question to find subject?
Who reading? This question has no answer. But every sentence has a subject. It means we are not asking the correct question. Now if we ask
What is a god habit? and the answer we get is Reading. It means "reading" is the subject of this sentence.
You must be wondering that read is a verb then why we are calling it as a subject [as the subject can only be a noun or pronoun]. You must notice that ‘read’ is attached with ‘ing’ and used as a subject. If a verb is added with ‘ing’ and used as a noun in a sentence, that verb is called ‘Gerund’.
I love you. [love as a verb]
Loving you is a part of my life. [Lov-ing as a gerund]
I think about them. [think as a verb]
Thinking so much is not good for health. [think-ing as a gerund]
I read books. [read as a verb]
Reading is a good habit. [read-ing as a gerund]
I run 5 kilometers a day. [run as a verb]
Running daily is good for health. [runn-ing as a gerund]
Rahul smokes. [smokes as a verb]
Smoking is injurious to health. [smok-ing as gerund]
Next Topic: Countable and Uncountable Nouns