fall off和fall down 有什么区别

all
down，fall
off和fall
over都表示“摔倒、跌倒”的意思，但它们各自的含义不同。
fall
over强调的是“向前摔倒、跌倒”。
she
fell
over
and
broke
her
leg.
她跌倒并把腿摔断了。
there
is
too
much
snow
on
the
ground.
if
you
ride
much
too
fast，you
will
fall
over.
地上的雪太多，如果你骑得太快的话，你会摔跤的。
fall
down强调的是“滑倒、倒下”，后接宾语时应加上介词from。
the
boy
hit
the
tree
to
hard
that
he
fell
down.
男孩重重地撞在树上，结果自己倒下了。
if
people
run
across
the
road，they
may
fall
down.
如果人们跑过马路的话，他们可能会摔倒。
fall
off强调的是“跌落、从……掉下来”，后直接接宾语。
the
girl
is
falling
off
the
bike.
（=
the
girl
is
falling
down
from
the
bike.）
女孩正从自行车上摔下来。
they
spread
a
big
net
in
case
tom
should
fall
off
the
tree
and
get
hurt.
他们张开一张大网以防汤姆从树上掉下来受伤。

fall off
decrease in quantity or quality 数量或质量下降: Attendance at my lectures has fallen off considerably. 听我讲课的人已大大减少了.
* It used to be my favourite restaurant but the standard of cooking has fallen off recently. 那是我以前最喜欢的饭馆, 但近来烹饪水平已大不如前了.

fall down
be shown to be false or inadequate; collapse 显示不实或不足; 崩溃; 失败: The plan fell down because it proved to be too expensive. 这项计划因费用过高而告吹.
fall down on sth (infml) fail to do sth properly or successfully 没有把某事做好: fall down on one's promises 未履行自己的诺言
* He fell down on the job. 他未能把这件工作做好.