until 与till用法的区别

till
/
until在表达方式和意义上的特殊性：until是till的强调形式，但是它们表达的意义是相同的，都表示"直到某时"。不过，当主句是否定句时，它引出的意思是"直到（某时）（某动作）才（发生）"
，这时候常会出现"not
until
…"的结构，如果将
"not
until
…"的结构放在句首，那么主句要写成倒装句。例如：
He
didn't
go
to
sleep
until
12
last
night
.
他昨晚直到十二点钟才睡觉。
They
didn't
realize
their
fault
till
we
pointed
it
out
to
them
.
直到我们向他们指出了他们的错误，他们才意识到。
Not
until
we
pointed
out
their
fault
to
them
did
they
realize
it
.
直到我们向他们指出了他们的错误，他们才意识到。
但是，当主句是肯定句时，它引出的意思是"直到（某时某动作停止了）"
。例如：
The
students
made
much
noise
till
the
teacher
came
into
the
classroom
.
直到老师走进教室学生们才停止了大声喧哗。
The
young
couple
were
very
happy
until
they
used
up
all
their
money
.
那对年青夫妇直到花光了所有的钱才沮丧起来。
另外，until
可以放在句首而till则不行。我们可以说：Until
they
used
up
all
their
money,
the
young
couple
were
very
happy
.我们却不可以说：Till
they
used
up
all
their
money,
the
young
couple
were
very
happy
.
此两个连词意义相同。肯定形式表示的意思是"做某事直至某时"，动词必须是延续性的。否定形式表达的意思是"直至某时才做某事"。动词为延续性或非延续性都可
以。
正确使用这两个连词的关键之一就在于判断句中的动词该用肯定式还是否定式。
肯定句：
I
slept
until
midnight.
我一直睡到半夜时醒了。
Wait
till
I
call
you.
等着我叫你。
（在肯定句中可用before代替
Let's
get
in
the
wheat
before
the
sun
sets.）
否定句：
She
didn't
arrive
until
6
o'clock.
她直到6点才到。
Don't
get
off
the
bus
until
it
has
stopped.
公共汽车停稳后再下车。
I
didn't
manage
to
do
it
until
you
had
explained
how.
直到你教我后，我才会做。
1)Until可用于句首，而till通常不用于句首。
Until
you
told
me,
I
had
heard
nothing
of
what
happened.
直到你告诉我以前，出了什么事我一点也不知道。
2)Until
when
疑问句中，until要放在句首。
---Until
when
are
you
staying?
你呆到什么时候？
---
Until
next
Monday.
呆到下周一。
注意：否定句可用另外两种句式表示。
(1）Not
until
…在句首，主句用倒装。
Not
until
the
early
years
of
the
19th
century
did
man
know
what
heat
is.
直到19
世纪初，人类才知道热能是什么。
Not
until
I
began
to
work
did
I
realize
how
much
time
I
had
wasted.
直到我开始工作，我才认识到了我已蹉跎了几多岁月。
(2)
It
is
not
until…
that…