～ないで

～ないで means "without doing": you do the second thing and leave the first undone. Take the ない-form of the verb and add で.

The tense comes at the end of the sentence. ～ないで itself never changes.

Instead of

～ないで also means "instead of": one choice is dropped and the other taken.

ないで or なくて

Both are the て-form of ない, and learners swap them. ないで goes with "without" and "instead of". なくて gives a reason: "because it didn't".

• × バスが来ないで、遅刻しました → バスが来なくて、遅刻しました

Asking someone not to do something

With ください after it, ～ないで makes a request not to do something. Among friends, ください drops off.