什么是实义动词，什么是现在完成时态｛英语】

实义动词，也叫行为动词。就我们现在所学的内容来讲，实义动词所在的句子中一般不存在be动词。也就是在含有实义动词的句子变否定句或疑问句时，一定不能用be动词。那么，实义动词究竟怎样用呢？正如be动词随着主语的变化可变为am、is、are一样，实义动词在肯定句中，也要随着主语的变化而变化。当主语为第三人称单数he,she,
it时，实义动词要变为相应的第三称单数；当主语为非第三人称单数I,
you(你),
we,you(你们)
they时，实义动词要用动词的原形。而在变否定句和疑问句时，不能直接在动词上变，而是要借助另一类动词：助动词do、does。
（1）肯定句：
①
I
have
a
blue
book.
②
He
has
a
brother.
③
She
wants
to
be
a
teacher.
④
They
like
to
play
basketball.
(2)否定句：主语+don’t/doesn’t+动词原形。其中do/does为助动词，是来帮助实义动词构成否定或疑问句的，但加了do/does后，其后面的动词必须用动词原形。
①
I
have
a
blue
book.（变为否定句）→I
don’t
have
a
blue
book.
②
He
has
a
brother.
（变为否定句）→He
doesn’t
have
③
She
wants
to
be
a
teacher.
（变为否定句）→She
doesn’t
want
to
be
a
teacher.
④
They
like
to
play
basketball.
（变为否定句）→They
don’t
like
to
play
basketball.
(3)一般疑问句：Do/Does
+主语+动词原形+其他？句中加了do/does后，其后面的动词还是必须用动词原形。
①
I
have
a
blue
book.(变为一般疑问句)→Do
you
have
a
blue
book?
②
He
has
a
brother.
(变为一般疑问句)→Does
he
have
a
brother?
③
My
brother
does
his
homework
before
supper.
(变为一般疑问句)
→Does
your
brother
do
his
homework
before
supper?
④
She
wants
to
be
a
teacher.
(变为一般疑问句)→Does
she
want
to
be
a
teacher?
⑤
They
like
to
play
basketball.
(变为一般疑问句)→Do
they
like
to
play
basketball?
(4)特殊疑问句：特殊疑问词+一般疑问句？
①
Your
sister
likes
English
best
because
it’s
interesting.
(对划线部分提问)
→Why
does
your
sister
like
English
best?
②
He
does
his
homework
before
supper.
(对划线部分提问)
→When
does
he
do
his
homework?
注意：当含有and引导的短语在句中做谓语或宾语，我们把这类句子变否定句时，必须把and变为or.如：
(1)He
can
swim
and
dance.
（变为否定句）→He
can’t
swim
or
dance.
(2)My
father
likes
English
and
math.
（变为否定句）
→My
father
doesn’t
like
English
or
math.

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