long before ，before long，long before then的意思，区别，用法？

Question

如题所述

Answer 1

before
long作“不久，很快”解，相当于soon，可用于过去时，也可用于将来时，而且只能单独作状语，后面不能接从句。如：
Before
long
he
had
to
move
on
again．
不久，他只得再次搬迁。
I
hope
to
see
you
again
before
long．
我希望不久可以见到你。
long
before作“在……以前很久、很久以前”解，可接从句，这时before为连词；如：
Mark
learned
to
read
long
before
he
started
school.
马克上学之前很早就学会了看书。
The
invention
had
been
widely
studied
long
before
it
was
put
to
use.
这项发明在投入使用前进行了广泛研究。
也可什么都不接，这时before是副词。如：
He
told
me
that
he
had
seen
the
film
long
before．
他告诉我他早就看过这部电影了。