section_path: Grammar/Verbs and verb phrases/Tense, aspect and mood
section_name: Tense, aspect and mood
paragraph_text: Tense, aspect and mood
  
  English has two primary tenses, past (preterite) and non-past. The preterite is inflected by using the preterite form of the verb, which for the regular verbs includes the suffix -ed, and for the strong verbs either the suffix -t or a change in the stem vowel. The non-past form is unmarked except in the third person singular, which takes the suffix -s.
  
  English does not have future verb forms. The future tense is expressed periphrastically with one of the auxiliary verbs will or shall. Many varieties also use a near future constructed with the phrasal verb be going to (" going-to future ").
  
  Further aspectual distinctions are shown by auxiliary verbs, primarily have and be, which show the contrast between a perfect and non-perfect past tense (I have run vs. I was running), and compound tenses such as preterite perfect (I had been running) and present perfect (I have been running).
  
  For the expression of mood, English uses a number of modal auxiliaries, such as can, may, will, shall and the past tense forms could, might, would, should. There are also subjunctive and imperative moods, both based on the plain form of the verb (i.e. without the third person singular -s), for use in subordinate clauses (e.g. subjunctive: It is important that he run every day; imperative Run!).
  
  An infinitive form, that uses the plain form of the verb and the preposition to, is used for verbal clauses that are syntactically subordinate to a finite verbal clause. Finite verbal clauses are those that are formed around a verb in the present or preterite form. In clauses with auxiliary verbs, they are the finite verbs and the main verb is treated as a subordinate clause. For example, he has to go where only the auxiliary verb have is inflected for time and the main verb to go is in the infinitive, or in a complement clause such as I saw him leave, where the main verb is see, which is in a preterite form, and leave is in the infinitive.