The subject (usually a noun or pronoun) is the part that the sentence is telling about. The subject is the noun or phrase that goes before the verb to show who is doing the action in an active sentence. e.g. John plays tennis every Saturday, or who or what the action is done to in a passive sentence. e.g. The food was cooked yesterday. The subject is the part of the sentence that performs an action or which is associated with the action. :subject: = :simple subject: | :compound subject:
The subject is the part of the sentence which performs an action or which is associated with the action.
When the form of the verb matches the person doing the action of the verb, e.g. I walk, he walks. If a learner writes
I walks, then it is wrong because there is no subject-verb agreement.