情态动词
【情态动词】
又叫情态助动词。它们具有以下特点:
⑴
它们必须与其他动词连用,即:情态动词+动词原形
表示说话人对所述动作的看法,如需要、可能、意愿或怀疑等。
⑵
绝大多数情态动词没有人称和数的变化,即第三人称单数不加-s
(以be和have
开头的情态动词短语除外)。
⑶
在意义上,情态动词具有“多义性”。
例:can既可表示能力,又可表示可能、允许等意义。
【情态动词的基本用法】
1.
can的基本用法:
⑴
表示体力或智力上的能力,即“能够,会”,可与be
able
to转换。
例:He
can
speak
English.
=
He
is
able
to
speak
English.?
—Can
you
play
basketball??
—
No,
I
can’t.?
如果表示将来具备的能力,要用will
be
able
to。
例:If
I
have
a
good
sleep,
I
will
be
able
to
do
the
problem.?
⑵
表示许可,主要用于口语,书面语一般用may。
例:—Can
we
go
home
now,
please??
—
No,
you
can’t.?
You
can
only
smoke
in
this
room.?
You
can’t
keep
the
library
books
for
more
than
a
month.?
⑶
表示“可能”,与may同义,但一般用在疑问句中。
例:What
can
he
possibly
want?
在否定句中,否定形式can’t表示推测“不大可能”。
例:Anybody
can
make
mistakes.?
The
news
can’t
be
true.?
与第一、二人称连用时,还可以就可能的解决问题的方式或可能的行为提出建议。在这里,也可用could使语气婉转。
例:Can
/
Could
we
meet
again
next
week??
下周我们可以再见面吗?
—What
shall
we
do??
我们怎么办呢?
—
We
can
/
could
try
asking
Lucy
for
help.?——我们可以请露茜帮忙试试看。
You
can
/
could
help
me
with
the
cooking.?
你可以帮我做饭。
2.
may的基本用法:
⑴
表示“许可”,用can比较口语化。
例:You
may
/
can
come
if
you
wish.?
如果你想来,你就来。
You
may
not
pick
flowers
in
this
park.
?本公园内不许摘花。
(may
not表示按规定不许可,如果用mustn’t则表示说话人不许可。)
—May
I
smoke
here??
我可以在这里抽烟吗?
—No,
you
mustn’t.?不行。(mustn’t表示明确的禁止。)
⑵
肯定句中表示推测,“可能”。
例:It
may
rain
tomorrow.?
明天可能会下雨。
The
news
may
not
be
true.?
这个消息可能不会是真的。
注意:如果在疑问句中表示“可能”,通常用can。
例:Can
it
be
true??
那会是真的吗?
Who
can
he
be??
他究竟是谁呢?
⑶
【注意】:—May
I/we……?
—Yes,
you
may./—No,
you
mustn’t.?
3.
must的基本用法:
⑴
表示必须,强调说话人的主观意志。
例:I
must
go
now,
or
I’ll
be
late.?
You
must
be
here
by
ten
o’clock.?
【注意】:表示“必须“时,must的否定式为needn’t
,或don’t
have
to
,而不是mustn’t。
也就是:—Must
I/we
do
it
now?
—Yes,
you
must
.
—No,
you
needn’t
/don’t
have
to
.?
例:—Must
I
go
with
them??
—No,
you
.?
⑵
表示推测,一般只用于肯定陈述句,表示非常肯定。
例:She
didn’t
look
at
me.
She
must
be
angry.?
她不朝我看,一定是生气了。
He
is
good
at
English.
He
must
know
the
word.?
他英语好,准知道这个词。
You
must
be
Mr.
Jones.?
想必您就是琼斯先生吧。
4.
have
to的基本用法:
have
to可视为情态动词,但它与其他情态动词在用法上稍有不同。其他情态动词没有人称和数的变化,而have
to却有人称和数的变化,要视主语的不同而变化。
例:I
/
You
/
We
/
They
have
to….
He
/
She
/
It
has
to….
You
don’t
have
to….
Does
she
have
to…?
have
to
=have
got
to,意思是“必须,不得不”。
和must不同之处:must强调主观需要
have
to强调客观需要。
例:Sorry,
I
have
to
leave
now.?
对不起,现在我得走了。
I’ve
got
to
go
to
a
meeting.?
我得去参加一个会议。
Will
he
have
to
work
deep
into
the
night??
他将不得不工作到深夜吗?
5.
need的基本用法:
need的基本词义是“需要”,它既可作情态动词,又可作实义动词。
⑴
need用作情态动词时,只用于否定句和疑问句。它只有一种形式,后接动词原形。
例:I
don’t
believe
you
need
worry.?
我相信你没有必要焦急。
—Need
we
go
so
soon??我们需要这么早就去吗?
—
Yes,
we
must.
/
No,
we
needn’t.??是的,必须。/不,不必。
So
I
needn’t
tell
him,
need
I??
所以我不需要告诉他,对吧?
请比较以下两句话的不同意思:
You
needn’t
buy
the
coat.?
你没有必要买那件外衣。(你还没买)
You
needn’t
have
bought
the
coat.?
你没有必要买这件外衣的。(而你却买了)
【注意】:—Need
I/we……?
—Yes,you
must
./—No,
you
needn’t
/
don’t
have
to
.
⑵
need用作实义动词时,有时态、人称和数的变化。
如果人作主语,一般后接带to的动词不定式。即need
to
do
sth;
如果物作主语,一般后用need
to
be
done
或need
doing
sth。
例如:I
need
to
look
up
this
word
in
the
dictionary.?
My
watch
needs
mending/to
be
mended.?
我的手表需要修理了。
We
don’t
need
to
work
today.?
(=
We
needn’t
work
today.)?
Does
he
need
to
go
right
now??
(=
Need
he
go
right
now?)?
6.
had
better的基本用法:
had
better常略作’d
better。现代语法认为它是一个助动词,因为它后接不带to的动词不定式。
had
better
do
sth意思是“最好做某事;还是做某事比较好”。
例:You’d
better
get
some
sleep.?
你最好睡一会儿。
You’d
better
not
do
that
again.?
你最好别再做那件事。
What
had
we
better
do
now??
我们现在怎么做才好呢?
Hadn’t
we
better
tell
her
the
truth??
我们是否最好不告诉她真相?
【注意】:You’d
better….表示劝告或委婉的命令,对长辈不宜使用。
7.?could,
should,
would,
might表示推测:
①.
must多用于肯定句中表示把握性极大的推测,意思为“一定、肯定”。
如:
You
have
worked
hard
all
day.
You
must
be
tired.
你已辛苦工作一整天了,一定累了。
The
book
must
be
his.
His
name
is
on
the
cover.
这本书一定是他的,封面上写着他的名字。
【注意】
must不表推测时,在肯定句中意思为“必须(强调内在的职责)”,在否定句中意思为“不许、禁止”,以它开头的疑问句否定回答常用needn’t或don’t
(doesn’t)
have
to。
如:We
must
obey
the
traffic
rules.
我们必须遵守交通规则。
Cars
mustn’t
be
parked
here.
此处严禁停车。
—Must
we
hand
in
the
papers
this
week?
我们必须本星期交论文吗?
—No,
you
needn’t.
不,你们不必(本星期交)。
②.
can
/
could多用于否定句、疑问句或感叹句中表示推测、怀疑,两者在时间上没有差别。用can时不相信的程度更强一些,
can’t常常译为“不可能”。
如:The
man
under
the
tree
can’t
be
Tom.
He’s
gone
to
England.
这个人不可能是Tom,他已经去英国了。
Can
it
be
true
that
he
was
fooled
by
a
five-year-old
boy?
他被一个五岁的孩子愚弄了,这能是真的吗?
Could
this
be
an
excuse?
这会不会是个借口?
How
can
you
be
so
careless!
你怎么这样粗心!
③.may
/
might多用来表示把握性不大的推测,意思为“也许、可能”,
might比may的把握性更小一些。
may
not在否定句中常常译为“可能不”。(注意区分“不可能”与“可能不”在把握性大小上的差异。)
如:Mr.
Wang
may
know
Professor
Li’s
telephone
number.王先生也许知道李教授的电话号码。
This
might
be
the
key
Tom
has
been
looking
for.这可能就是汤姆一直在找的钥匙。
She
may
not
be
there
today.
今天她可能不在那儿。
1、
典型例题
【中考链接】
(
)1.—Who
is
the
man
over
there?
Is
it
Mr.
Li??
—
No,
it
______
be
him.
Mr.
Li
is
much
taller.
A.
mustn’t
?B.
may
no
C.
can’t
?
D.
needn’t
(
)2.—Must
I
go
with
them
tomorrow?
—
No,you
______.
A.
mustn't?
?
B.
shouldn't?
?
C.
needn't?
?
D.
can't
(
)3.—______
I
take
some
photos
in
the
hall??
—
No,
you
______.
A.
Can,
needn’t?
B.
Must,
mustn’t
C.
Could,
won’t
D.
May,
mustn’t
(
)4.—Dad,
must
I
finish
my
homework
today?
—No,
you
________.
You
may
do
it
tomorrow.
A.
needn’t
B.
mustn’t
C.
don’t
D.
won’t
(
)5.—The
lake
is
said
to
be
dry.
Is
that
true?
—It
_______.Look,
some
kids
are
swimming
in
it.
A.
must
be
true
B.
can’t
be
true
C.
may
not
be
true
(
)6.—What
is
your
mother
going
to
do
this
Saturday?
—I’m
not
sure.
She
_____
go
to
see
my
grandmother.
A.
can
B.
must
C.
may
(
)7.—Susan
has
bought
a
large
house
with
a
swimming
pool.
—It
______
be
very
expensive.
I
never
even
dream
about
it.
A.
must
B.
might
C.
can’t
D.
shouldn’t
(
)8.—Listen!
Is
Professor
Johnson
giving
a
report
in
the
hall?
—No,
it
be
him.
He
has
gone
to
Japan.
A.
needn’t
B.
may
not
C.
mustn’t
D.
can’t
(
)9.—Let’s
go
to
the
West
Hill
Park
by
taxi.
—Oh,
it
is
not
far
away
from
here.
We
_______take
a
taxi.
A.
couldn’t
B.
mustn’t
C.
needn’t
D.
can’t
(
)10.—Can
you
play
the
piano?
—Yes,
I
_______.
I
often
practice
it
on
weekends.
A.
needn’t
B.
need
C.
can’t
D.
can
三、课后练习
一、用can,
may,
must,
need,
have
to,
had
better的适当形式填空:
1.?
You
________________
return
the
library
book
on
time.
2.?
I
______________
(not)
find
the
way
to
the
hospital.
_______________
you
show
me
the
way?
3.???
—________________
I
finish
the
work
right
now?
—
No,
you
________________
(not).
You
____________
do
it
later.
4.??
He
said
he
________________
(not)
come
tonight.
5.?
Her
mother
was
ill.
She
________________
stay
at
home
and
look
after
her.
6.???
It’s
time
for
class.
You
________________
stop
playing
football
or
you
__________be
late
for
class.
7.??
We
________________
start
right
now,
or
they
would
get
there
first.
8.??
The
cloud
is
lifting,
so
it
________________
(not)
be
a
rainy
day
tomorrow.
二、选择填空
(
)1.—Do
we
have
to
finish
our
homework
this
afternoon?
—Yes,
you
________.
A.
must
B.
can
C.
may
D.
need
(
)2.
—Must
I
be
in
hospital
for
a
week,
Doctor??
?
—No,
you
?????.
You
can
go
back
home
tomorrow.?
A.
mustn’t???????
B.
needn’t???
C.
must?
(
)3.
The
desk
is
not
dirty.
You
_______clean
it.
A.
mustn’t
B.
shouldn’t
C.
needn’t
C.
can’t
(
)4.
—May
I
watch
TV
for
a
while?
—No,
you
_______.
You
have
to
finish
your
homework
first.
A.
shouldn’t
B.
needn’t
C.
mustn’t
D.
won’t
(
)5.—Is
Jessica
giving
us
a
speech
this
evening?
—No,
it
________be
her.
She________
to
Japan.
A.
mustn’t;
has
gone
B.
mustn’t
;has
been
C.
can’t
;has
gone
D.
can’t
;has
been
(
)6.
It’s
the
library!
So
you________
know
shouting
is
not
allowed
here.
A.
can
B.
must
C.
need
D.
may
(
)7.
Boys
and
girls,
don’t
forget
your
report
.
It
______
today.
A.
can’t
finish
B.
can’t
be
finished
C.
should
finish
D.
should
be
finished
(
)8.—Mr
Smith
must
have
been
to
your
home
this
morning.
—No,
he
______
,because
he
didn’t
know
my
address.
A.
couldn’t
B.
can’t
C.
mustn’t
D.
may
not
(
)9.
—Must
I
mop
up
the
window
now?
—No,
you________.
A.
needn’t
B.
can’t
C.
shouldn’t
D.
mustn’t
(
)10.
—Is
Lucy
knocking
at
the
door?
—No.
It
________
be
Lucy.
She
is
in
Japan
now.
A.
needn’t
B.
must
C.
can’t
(
)11.
—Another
cup
of
coffee?
—No,
thanks.
I
_____
be
off.
Mary
is
waiting
for
me.
A.
can
B.
may
C.
must
D.
might
(
)12.
—I’m
a
little
tired.
Let’s
go
to
the
zoo
by
taxi.
—We
take
a
taxi.
It’s
not
far
from
here.
A.
can’t
B.
mustn’t
C.
couldn’t
D.
needn’t
(
)13.
If
the
traffic
light
is
red,
you
________
cross
the
road.
It’s
very
dangerous.
A.
don’t
B.
mustn’t
C.
needn’t
D.
wouldn’t
(
)14.
—Must
I
finish
watering
the
flowers
now?
—No,
you________.
A.
must
B.
won’t
C.
needn’t
D.
can’t
(
)15.
—I
can’t
give
up
smoking,
doctor.
—For
your
health,
I’m
afraid
you
________.
A.
may
B.
can
C.
have
to
D.
must
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1