情态动词的用法:
can
(could)
表示说话人能,可以,同意,准许,以及
客观条件许可,could
为
can
的过去式。
Can
you
pass
me
the
books?
你能给我递一下书吗
?
Could
you
help
me,
please?
请问,你能帮助我吗?
What
can
you
do?
你能干点什么呢?
Can
you
be
sure?
你有把握吗?
can
和could
只能用于现在式和过去式两种时态,将来时态用
be
able
to
来表示。
He
could
help
us
at
all.
他完全可以帮助我们。
With
the
teacher's
help,I
shall
be
able
to
speak
English
correctly.
由于老师的帮助,我将能准确地讲英语。
may
(might)
可以,
表示说话人同意,许可或请求对方许可。
You
may
take
the
book
home.
你可以把书带回家去.
May
I
come
in?
我可以进来吗?
May
I
use
your
dictionary
?
我可以用你的词典吗?
You
may
put
on
more
clothes.
你可以多穿点衣服.
He
said
he
might
lend
us
some
money.
他说他可以借给我们一些钱。
may
否定式为
may
not,
缩写形式是
mayn't.
might
是may
的过去式,
有两种用法,
一种表示过去式，一种表示虚拟语气,
使语气更加委婉,
客气或对可能性的怀疑。
He
told
me
he
might
be
here
on
time.
他说他能按时间来。
Might
I
borrow
some
money
now.
我可以借点钱吗?
He
might
be
alive.
他可能还活着。
Must
必须,应该,一定,准是,
表示说话人认为有必要做某事,
命令,
要求别人做某事以及对事物的推测。
must
用来指一般现在时和一般将来时,
过去式可用
have
to
的过去式代替。
I
must
finish
my
work
today.
我今天必须完成我的工作。
You
mustn't
work
all
the
time.
你不能老是工作。
Must
I
return
the
book
tomorrow?
我必须明天还书吗?
After
such
a
long
walk,
you
must
be
tired.
走了这么长的路,你一定困了。
He
must
be
the
man
I
am
looking
for.
他一定是我要找的人。
He
had
to
go
because
of
somebody's
calling
him
that
day.
那天他要走是因为有人叫他。
must
+
have
+
过去分词,表示现在对过去事物的推测。
He
must
have
told
my
parents
about
it.
他一定把这件事情告诉我父母亲了。
He
must
have
received
my
letter
now.
他现在一定收到我的信了。
It's
six
o'clock
already,
we
must
have
been
late
again.
已经六点钟了，我们一定又迟到了。
must
和
have
to
的区别:
must
表示说话人的主观思想,
have
to
表示客观需要。
You
must
do
it
now.
你必需现在就干。(说话人认为必须现在干)
I
have
to
go
now.
我得走了。(客观条件必须现在走)
need
需要
多用在否定式或疑问句中.
Need
I
attend
the
meeting
tomorrow?
我需要明天参加会议吗?
You
need
not
hand
in
the
paper
this
week.
这一周你不必交论文。
need
是一个情态动词,
他的用法完全和其他情态动词一样,
但
need
还可当作实义动词使用,
这时
need
就象其他动词一样,有第三人称,单复数,
后面加带
to
的动词等特性。
I
need
a
bike
to
go
to
school.
我上学需要一辆自行车。
Do
you
need
a
dictionary?
你需要词典吗?
She
needs
a
necklace.
她需要一条项链。
needn't
+
have
+
过去分词
表示过去做了没必要做的事情。
You
needn't
have
taken
it
seriously.
这件事情你不必太认真。
dare
敢
多用在否定或疑问句中。
The
little
girl
dare
not
speak
in
public.
小女孩不敢在公众面前说话。
Dare
you
catch
the
little
cat?
你敢抓小猫吗?
dare
除用作情态动词外,更多的是当实义动词使用,
用法同实义动词一样,要考虑人称,单复数,时态等。
Do
you
dare
to
walk
in
the
dark?
你敢黑夜走路吗？
He
doesn't
dare
to
tell
the
teacher
what
happened
that
day.
他不敢告诉老师那天发生的事。
ought
应当,应该
后面跟带有
to
的动词不定式。
You
ought
to
read
these
books
if
you
want
to
know
how
to
repair
the
motorcar.
如果你想知道如何修理汽车,你应该读这些书。
You
ought
to
bring
the
child
here.
你应该把孩子带来。
ought
+
to
have
done
句型。指过去动作,表示一件事情该做而未做。
You
ought
to
have
been
here
yesterday.
你昨天就应该来。
ought
not
to
have
done
句型。表示一件不该做的事情却做了。
You
ought
not
to
have
taken
the
book
out
of
the
reading-room.
你不应该把书带出阅览室。
will
(would)决心,愿望。
would
为
will
的过去式,
可用于各人称。
I'll
do
my
best
to
catch
up
with
them.
我要尽全力赶上他们。
I'll
never
do
it
again,
that's
the
last
time.
我再不会做那件事情了,这是最后一次。
He
said
he
would
help
me.
他说他会帮助我。
will,
would用于疑问句表示说话人向对方提出请求或询问,用
would
比
will
更婉转,客气。
It's
hot.
Will
you
open
the
windows?
天气太热了,你能打开窗户吗?
Will
you
help
me
to
work
it
out?
你能帮我解这道题吗?
Would
you
like
some
coffee？
给你来点咖啡怎样？
Shall,
should表示命令,警告,允诺,征求,劝告,建议惊奇。
You
should
hand
in
the
exercise
book.
你应该交作业本儿了。
This
should
be
no
problem.
这应该没问题。
Shall
we
go
now.
我们现在可以走了吗?
Why
should
I
meet
him？
为什么我要见他?
have
to,不得不,必须,表示客观条件只能如此,
而must
则表示主观思想必须。
I
have
to
go
now.
我现在得走了。
I
have
to
cook
for
my
child.
我得给孩子做饭。
You
must
be
here
on
time
next
time.
你下次一定要按时来。
We
must
go
to
get
the
timetable
ourselves.
我们一定要自己去拿时刻表。
参考资料：
http://www.cnread.net/cnread1/yyxx/yyyf/008.htm