Subject (grammar)

The subject in grammar is the agent (the 'doer') in an active sentence such as: Alan kissed Jane.

However, there is a difficulty. The following two sentences are identical in meaning:
Our children planted a tree. 
A tree was planted by our children.
Only in the first sentence is our children the grammatical subject. So there is a difference between the logical subject and the grammatical subject.McArthur, Tom (ed) 1992. The Oxford companion to the English language. Oxford University Press.p996 Also, many sentences have no subject, for instance:
Come here!
Identifying the thief may take some time.

If a sentence does have a subject, then the rest of the sentence may be called the predicate. 

 References 

Category:Grammar