不定式作表语表示具体动作或将来动作;动名词作表语表示抽象的一般行为.
①To
be
kind
to
the
enemy
is
to
be
cruel
to
the
people.
②My
chief
purpose
is
to
point
out
the
difficulties
of
the
matter.
③What
I
would
suggest
is
to
put
off
the
meeting.
当主语和表语都是不定式时,其含义一是条件,一是结果(例①).当主语是aim,
duty,
hope,
idea,
mistake,
plan,
purpose,
suggestion等为
中心词的名词词组(例②)时,或以what引导的名词性分句(例③),不定
式说明主语的内容.
④Our
work
is
serving
the
people.
⑤What
he
likes
is
taking
a
walk
after
supper.
⑥The
story
told
by
Mr.
Wang
is
interesting.
④⑤句动名词作表语,与主语部分可以转换,如Serving
the
people
is
out
work,
而⑥句中是现在分词作
表语,说明主语的性质,状态,现在分词具有形容词的各种特征,另外,动名词作表语还应与进行时态区别开来.