Time is a concept which is related to our perception of reality. There are three times: past, present and future. Tense is a grammatical category which is marked by verbA part of speech that expresses an action or a state. E.g.: John seldom plays tennis. inflectionA change in or addition to the form of a word that shows a change in the way it is used in sentences. E.g.: He likes what you cooked. ("-s", "-ed") and expresses when an eventA general term expressing that somebody or something does something or that something happens. E.g.: An apple fell on Isaac’s head. or actionA general term expressing that somebody or something does something happens in the flow of time.