How to Use Verb Tenses
The twelve verb tenses (or tense-aspect combinations) are used to specify when and how an action occurs.
Verb Tense tells us when:
Verb Aspect tells how in relation to time:
Continuous = action is ongoing
Perfect = action is complete
Perfect Continuous = action is ongoing up until some point (*except in present tense, see below)
Simple = The verb itself does not indicate if the action is ongoing or complete. It only indicates the bare tense: past, present, future.
Details below, but here are a few cheat sheets (right click and save):
is used to talk about facts, habits, and actions that are happening now or repeating.
I kill people on Tuesdays.
[Root form of verb. If in third person singular, add s/es to the end]
She kills people all the time.
She bashes his head in with a meat cleaver.
is used to describe actions that happened at an unspecified time in the past. The action is either complete or continues up to the present.
I have killed before.
He has killed six people.
[have/has + past participle] See here for more on participles.
NOTE: If you need to specify a time, do not use Present Perfect, e.g., I have killed yesterday is incorrect. Instead, use Simple Past Tense (see below).
is used to describe actions that are ongoing at present.
I am killing someone at the moment.
We are killing this pizza.
[am/is/are + present participle (the ing form of the verb)]
Present Perfect Continuous
is used to describe ongoing actions that started in the past and are still ongoing at present.
She has been killing people for seventeen years. (She is still killing people.)
[has/have been + present participle]
is used to describe actions that happened in the past, past habits, or a past state of being. Unlike Present Perfect, time can be specified.
He killed everyone last night.
[Root form of verb + ed, or just d if the word ends with e] See here for exceptions.
is used to describe actions that completed before some other action or time in the past.
He had killed them all before the police arrived.
[had + past participle]
is used to describe an action that was ongoing for some duration of time in the past (often emphasizing an interruption) or actions that were happening at the same time in the past.
She was stabbing the man when the police walked in.
The police were coming up the stairs while she was stabbing the man.
[was/were + present participle]
Past Perfect Continuous
is used to describe an action that was ongoing in the past and ended at some point also in the past.
I had been killing people for seventeen years when the police caught me.
[had been + present participle]
is used to describe actions that will happen in the future.
I will kill them all tomorrow.
[will + root form of verb]
is used to describe actions that will be completed before some other act or time in the future.
I will have killed them all by the time you get here.
[will have + past participle]
is used to describe an ongoing action that will occur in the future.
They will be celebrating their kills tomorrow evening.
[will be + present participle]
Future Perfect Continuous
is used to describe ongoing action that will be completed by some specified time in the future.
I will have been killing for seven years by the time Christmas arrives.
[will have been + present participle]