Time, tense and aspect

It is important not to confuse time and tense. Time is universal non-linguist concept with three dimensions: past, present and future. However, the tense does not always refer to its supposed time (I leave tomorrow = the tense is present but the sentence refers to the future.) Verb phrases can either be marked for tense or have a modal verb. Not both! There is no way to mark future tense on verbs in English – they cannot be inflected for future in the same way they are for present of past tense. Instead, it’s marked with a modal (will, shall) or semi-modal (be going to).

 Simple present tense has three major meanings when it refers to present time.

1. Describes a state that exists at the present time, the state may be temporary or it may last for longer time. (I want a new computer.)

2. It can also refer to habitual action that is repeated on occasion, rather than state of being (She is a vegan but she drinks milk.)

3. It can describe an action that is happening at the present time (Here comes your mother.)

Simple past tense most often refers to past time. It can also give information about stance in present, usually with verbs think, wonder and want. (I just wanted to thank you.) Hypothetical conditions can be also expressed. (It’s time you got married.) It has special use in reported speech. (He said he would do it.)

Aspect

Aspect can be progressive or perfect. Aspect answers the question "is the event/state described by verb completed or is it continuing?" Progressive and perfect aspects are usually combined with present or past tense.

Perfect aspect, present tense (We have written to her.) Perfect aspect, past tense (He had seen him picking purses.) Progressive aspect, present tense (Jeff is growing his beard.) Progressive aspect, past tense (I was thinking about it.)

Progressive aspect refers to ongoing, uncompleted action and consists of the auxiliary be form and the -ing form of the lexical verb. (is seeing, are arriving).

Perfect aspect is created by the auxiliary have and the third participle form of the lexical verb. It describes events or states taking place during a preceding period of time. (Contrast "The flowers didn't bloom this summer" with "The flowers haven't bloomed this summer." = The latter sentence suggests that the summer is not over yet.)