Name: Perfect Aspect | The parts of speech | Grammar | Khan Academy
Uploaded: 2018-07-27T05:17:26.000Z
Duration: 2 min 31 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

To-infinitive

- [Voiceover] Hello grammarians,
today I want to talk to you

about the idea of the
perfect aspect of verbs.

And what that means is
that it's not, you know,

beyond reproach, or that it's
like beautiful and shiny.

What it means is really that
whatever we're talking about,

whatever action we are
talking about is complete.

So we use the perfect aspect in all tenses

to illustrate when
something has been completed

But when we're using, when we use aspect,

it enables us to talk about a
period between then and now.

You're speaking in the now
referring to a point previous.

the way you form the perfect
is you simply add have

and then you use the
past form of the verb.

So if my assignment, for example,
were to wash some dishes,

when the dishes were complete,
I would say to the person

that told me to wash the dishes,
"I have washed the dishes."

So I'm using the present
tense form of to have,

the thing that changes is the helper verb.

This part, the main verb, does not change.

we're talking about the
present or the future.

So if we want to put
this story in the past,

you know, talk about a period
that is "then" but also say

that we washed the dishes at
a period before then, right,

before the moment in the past
that we're talking about,

And if we want to talk about
something in the future

that happens before that
future moment but after now,

And that's what the perfect
aspect allows us to do.

It allows us to travel backward
in time a little bit extra.

It allows us to say, oh, well,
before the point in the story

that I'm mentioning, this
thing was already completed.

So the perfect enables us
to say, here is a thing

that happened in the past,
here is a verb action

So to recap, the perfect
refers to something finished.