efore 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.