appointment 和 date 都有约好时间见面的意思
date 一般指男女之间约会
appointment 没有男女约会这个意思
例句：
I have a doctor's appointment at 9am tomorrow.
I have a date with a cute guy tomorrow.
date 也可以做动词
Who are you dating these days?
go out 出去,有时也指男女约会
例句,男孩问女孩：
Would you like to go out with me?