我們先把nearly挑出來說，nearly與almost 可互換。是“幾乎”的意思。

但表否定時，nothing, no 之前 不能用nearly, 應用almost。或用hardly any-代替

The room is nearly empty.

The driver was nearly dead…

不能說There"s nearly no one left.

應說：there"s almost no one left.

或：there"s hardly anyone left.

再看near, nearby 和near by

near可表示時間、空間、程度等方面的接近。

nearby和near by只能表示空間上的接近，也就是“附近”。

所以你的疑惑應該是在表示空間接近時該用哪個吧

near可作表語、前置定語、狀語，

nearby可作定語（前置後置都可以）、狀語，

near by可作表語、定語（僅後置）、狀語。

作表語時，near vs near by

near與near by可互換。如The restaurant is near.（最常用啦）

=

The restaurant is near by.

作前置定語時，near vs nearby

near不會以原形出現，而是以比較級/最高階形式出現，如

It took us 1.5 hours to get to the nearest hotel.

而nearby壓根沒有比較級和最高階。如

They moved to a nearby town.

作後置定語時，nearby vs near by

可互換，幾無差別。如the shop nearby=the shop near by.

作狀語時，near vs nearby vs near by

一般可互換，個人感覺不必太在意。

如She lives near=She lives nearby.There is a new theatre near our house.=There is a new theatre near by our house.