The label 16 English tenses describes a teaching framework: four time-reference groups, each with simple, continuous, perfect and perfect continuous forms. Many courses teach 12 main forms and discuss future in the past separately. Strictly speaking, English verbs have present and past tense inflections; future meanings use constructions such as will.
Across these groups, simple forms present situations without continuous or perfect marking. Continuous forms highlight activity in progress. Perfect forms look back from a reference point. Perfect continuous forms combine that backward view with an emphasis on ongoing activity or duration.
Present
- Simple: I work can describe a habit or regular situation.
- Continuous: I am working describes activity happening now or around now.
- Perfect: I have worked here before connects past experience with the present.
- Perfect continuous: I have been working for two hours emphasizes activity over a period leading up to now.
Past
- Simple: I worked yesterday places an event in a finished past period.
- Continuous: I was working when you called shows activity in progress at a past moment.
- Perfect: I had worked there before we met looks back from a later past point.
- Perfect continuous: I had been working for hours when you arrived emphasizes duration before that point.
Future
- Simple: I will work tomorrow expresses a future situation.
- Continuous: I will be working at noon presents activity in progress then.
- Perfect: I will have finished by noon looks back from a future deadline.
- Perfect continuous: I will have been working for six hours by noon emphasizes duration up to that point.
Future in the past
These forms describe something viewed as future from a past perspective. Compare She said she would work, would be working, would have worked and would have been working. The perfect forms look toward completion or duration before a later reference point. These patterns also occur in conditional sentences, but would does not always express a condition. Context determines the meaning.