until、after、before和since的区别、用法和意思

这三个介词主要区别如下：
before意思是“在...之前”
he
arrived
before
me.
他在我之前到达.
after意思是“在...之后”
c
comes
after
b
in
the
alphabet.
在字母表中c接在b后面.
until意思是“直到...时”
until
she
spoke
i
hadn't
realized
she
was
foreign.
她要不说话我还一直不知道她是外国人.