backup
n. C / Un. a copy of important files or data kept in a safe place in case the original is lost. It can also mean a person or thing that is ready to help if the main one fails.
n. a copy of data or files stored separately from the original to ensure recovery after a loss; by extension, a person or thing that serves as a substitute or support.
You should always keep a backup of your photos on a hard drive.
The IT department runs a full system backup every Friday night to prevent data loss during the weekend.
While the primary server handles the bulk of the traffic, the secondary unit serves as a critical backup to maintain uptime during unexpected hardware failures.
Deverbal from back up.
Often used as a compound noun; when used as a verb, it is written as two words ('back up').
I need to backup my filesI need to back up my filesThe single word 'backup' is a noun; the action requires the two-word phrasal verb 'back up'.