Every sentence has two parts: the subject, which names the person or thing being spoken about, and the predicate, which tells something about the subject. While the subject usually comes first, it can occasionally come after the predicate. In imperative sentences, the subject is left out but understood to be "you". A sentence needs both a subject to speak about and a predicate to say something about that subject.

1. Subject and Predicate

2. Every sentence has TWO parts
1. The part which names the person or thing
we are speaking about is called the Subject of
the sentence.
2. The part which tells something about the
Subject is called the Predicate of the
sentence.

4. The Subject of the sentence usually comes
first, but occasionally it takes place after the
Predicate.
Here comes the bus. - The bus comes here.
Sweet are the uses of adversity.
Just around the corner was the parade.

5. In Imperative sentence the Subject is left out
(hidden), and it is understood.
Sit down.
Thank you.
Please open the door.

6. In other words, we must have a subject to
speak about and we must have a predicate
about that subject.