beforehand

Compared meaning: earlier than a particular time (adverb).

比较义项：提前，预先（副词）。

• ahead

  Ahead usually combines with 'of' plus a time reference (ahead of schedule/time) or follows verbs like plan, think, book; it also has an unrelated spatial sense (in front), not compared here.

  ahead 通常与“of + 时间”搭配（ahead of schedule／ahead of time），或跟在 plan、think、book 等动词后面；它还有一个不在此比较的空间义，表示“在前面”。

  We finished the renovation three days ahead of schedule.

  我们比计划提前三天完成了装修。

• beforehand 本词

  Beforehand refers to before a specific event or time and typically stands alone at the end of a clause, without 'of'; it has no spatial meaning and no fixed collocation with verbs like plan.

  beforehand 指在某个具体事件或时间发生之前，通常单独放在句末，不与 of 连用；它没有空间义，也不像 ahead 那样固定搭配 plan 之类的动词。

  Could you tell me beforehand if the flight gets delayed?

  如果航班延误，你能预先告诉我吗？

Ahead and beforehand both mean earlier than a particular time. Ahead goes with 'of' (ahead of schedule) or follows verbs like plan or book; it means 'in front', not compared here. Beforehand means before a specific event and stands alone at the end, without 'of'.

这两个词在“提前、预先”这个意思上很接近，但用法不同：ahead 常与“of + 时间”搭配（ahead of schedule／ahead of time），或跟在 plan、think、book 等动词后面，表示笼统的“提前做某事”；beforehand 则专指在某个具体事件或时间发生之前，通常单独放在句末，不与 of 连用。这里不比较 ahead 表示方位“在前面”的空间义。