The formal sign of the opposition constituting this category is, with regular verbs, the dental suffix -(e)d [-d, -t, -id], and with irregular verbs, phonemicinterchanges . Thus, the opposition is expressed by the formula
THE PAST TENSE (past) VS. THE PRESENT TENSE (non-past)
The structural nature of the expression of the category of primary time is the only immanent verbal category expressed by inflexional forms. These inflexional forms (the past and present) coexist with the other, analytical modes of categorial expression, including the future.
Hence, the English verb acquires the two futures:
| PRESENT Jill returns from her driving class at five o'clock. | PAST At five Jill returned from her driving class. I know that. | ||
| FUTURE I (the future of the present prospected from the present) Jill will return from her driving class at five o'clock. | FUTURE II (the future of the past prospected from the past) I knew that at five Jill would return from her driving class. | ||
This system is marked by the do-forms of the indefinite aspect found in the interrogative constructions (Does he believe the whole story?), in the negative constructions (He doesn't believe the story), in the elliptical response constructions and elsewhere and confined only to the category of primary time (the verbal past and present not the future).
The existence of future tenses is not universally recognized since what is described as the future tense in English is realized by means of auxiliary verbs will and shall. Although it is undeniable that will and shall occur in many sentences that refer to the future, they also occur in sentences that do not. And they do not necessarily occur in sentences with a future time reference. That is why future tenses are often treated as partly modal.
Although the future of the English verb is highly specific as its auxiliaries in their etymology are words of obligation and volition on the whole, the English categorial future differs distinctly from the modal constructions with the same predicator verbs.