An ELT Glossary : Tense

• Definition : An attribute of the verb system which is indicated by the potential presence of morphological marking of the base verb

• Example :  play/plays vs played,  have/has vs had, will vs would 

• Any English verb form will have tense as one of its attributes (others being aspect and voice) and this is generally indicated by the name commonly given to the verb form - eg present continuous, past perfect

• As these names indicate, tense is often seen as having the primary function of indicating time relationships. However,  this is misleading in many languages, including English, where as Lewis points out, it is better seen as implying immediacy versus remoteness. This "remoteness" may be 

        a) immediacy or remoteness in time (He is here vs He was here) 

        b) psychological immediacy or remoteness (I want to ask you something as                 opposed to I wanted to ask you something...) 

        c) immediacy of or remoteness from reality (John is here. He can help with                   this  as  opposed to  I wish John was here. He could help with this)

• All these examples refer to English, showing that English has two tenses. Other languages may have more (eg Italian has a verb form which conveys future meaning through tense) or none, eg Chinese. 

• The term "tense" is often used incorrectly to refer to any verb form - eg *the present perfect tense. This is a misuse of the term. As we said above, verb forms have tense as one of their features, but calling verb forms like the present perfect, simple present, past continuous etc "tenses" is a misuse of the term.

Reference

Lewis, M. (1986) The English Verb, Cengage Learning EMEA