Modal verbs | The parts of speech | Grammar | Khan Academy Video Lecture | Complete Course on English Grammar: Upgrade your Speaking & Listening - Personal Skills

hello grammarians today we're going to
talk about a class of auxiliary or
helper verbs called the modal verbs
these are verbs that have special
properties and help other verbs but what
is modality my fellow grammarian I am so
glad you asked
modality is when we use these verbs to
express conditions on stuff so we can
use these verbs to determine if
something is likely to happen or certain
to have happened whether or not
something is possible or whether or not
we have the ability to do something
whether or not we have the permission to
do something and whether or not we have
the obligation or requirement or need to
do something you already know all of
these verbs I promise you you just
didn't know this name for them let's
meet the modal's roll call here we go
may might must can could shall should
will would those are the modal's so
here's what modal verbs can do think
number one they agree with everything so
you can take any one of these modal's
and you can use any subject in the world
and it's not going to change right you
take a word like talk for instance and
you can say I talk Dian talks right you
have the S but any subject in any
sentence is going to take the modal verb
the same way let me show you I can do it
you can do it she can do it they can do
it we can do it it's all the same they
agree with everything
something else that modal's do is
actually something that they don't do
they don't have a to form this is what
we call the infinitive so there's no
such thing as two Mei or two could that
just doesn't exist so modal's don't have
infinitives you can't say I want to
should it doesn't that is an illegal
operation in English it is ungrammatical
it doesn't matter what version of
English you speak across all varieties
of English you cannot to should and
finally a thing the modal verbs can do
is indicate modality which like we said
establishes conditions so let's take a
look at some examples so the word must
right we can use the word must in a
couple of different ways so if you
imagine a detective looking up from some
tracks some muddy boot prints on the
floor with her magnifying glass she
looks up and she says he must have gone
that way that Detective is saying is
using must to express like a likelihood
of high likelihood this must have
happened but if you're at an amusement
park and the roller coaster you want to
ride has a height requirement the sign
probably says you must be this tall to
ride the doomed coaster this is like a
necessary condition by a similar token
if you enter someone's house and they
demand that you take off your shoes they
would say you must remove your shoes
similarly with May we can use May to
express a possibility like saying it may
rain that's something that could
possibly happen or to give someone
permission like you may enter you can
use a word like can to express ability
you could say I can eat ten pounds of
broccoli and that's expressing your
ability to do a thing we also use modal
verbs like this to talk about conditions
or stuff that isn't going to happen or
maybe could happen and so it for example
in this sentence we would say I would
make the bed but I'm tired because the
possibility exists however remote that
the bed would be made by me but I'll
feel like it so I'm using wood to offer
an excuse I'm saying this could possibly
happen this would happen except for this
one other problem which is that I'm
sleepy you can also use modal verbs to
give advice to someone as in you
shouldn't do that and something that is
special to will and to a lesser extent
shall is that they can form the future
shall used to be a lot more popular and
it still is in British English but less
so in
American so you would say he will win
the competition or he shall win the
competition and use of this modal verb
will or shall indicates that that thing
that you're talking about is happening
in the future these verbs are very
powerful you should learn how to use
them and in fact if you can complete the
exercises then you will master these
tricky verbs you can learn anything Dave
it out