English Tenses and Sentence Structure
I. Subject: A noun or pronoun which performs an action or is introduced to us in a given sentence is called a subject.
a) He is working on the papers. (Here He, a pronoun, performs the action of Working).
b) My car has broken down on the subway. (Here My car, a noun phrase, is a being introduced to us.)
II. Object: A noun or pronoun which is worked upon or which is referred to for the action being performed in a given sentence.
a) He is working on the papers. (Here the action is being performed on the word papers, a noun.)
b) He is going to school. (Here, no action is being performed on the word School, a noun; however, the action being done by subject is related to the word school.)
III. Helping Verb(also called linking/auxiliary verb): These are linking words besides differentiation of sentences into various tenses while making them sound meaningful for intended purposes e.g. be, was, were, been, had, has, have, will, shall etc.
IV. Verb (and its forms): Verb is a word which shows an action or relates an activity.
What we need to remember for correct formation of tenses? The answer is somewhat straightforward; learn basic verbs with spelling, meaning and forms as well as linking verbs for each type of tense in order to express in grammatically correct English. We must be able to identify which is our intended subject, object, verb or time from among the various words of a sentence at hand.