备用 (bèi yòng): Reserve (Verb) — Meaning & Stroke Order

I'll give you the spare key to keep, just in case I forget mine.

He secretly gave the spare key to his friend, which made me very angry.

After receiving the power outage notification, we immediately prepared a backup power source.

If there is a traffic jam, do we need to meet at the alternate location?

I usually keep a spare charger in the office just in case.