What does backup mean?
A backup is a reserve copy of data, a person, or equipment held ready in case the original fails, is damaged, or needs reinforcement. In modern usage the word is dominated by computing: backing up files means creating duplicates on an external drive or in the cloud so that nothing is lost if a device crashes or data is corrupted. The term also survives in everyday speech through phrases like 'call for backup,' where it refers to summoning extra help or support, a usage rooted in police and military language. More broadly, a 'backup plan' is any alternative course of action kept in reserve should the primary one fail. The word conveys prudence and foresight — having a backup suggests careful planning — though it can also imply that failure was anticipated. Related chiefly to the verb phrase 'back up,' which describes both making a copy and moving in reverse, 'backup' is indispensable vocabulary in both technical and everyday English.
A reserve copy of data or a reserve resource, person, or piece of equipment available if the original fails or extra support is needed.
"The IT team restored the system from last night's backup."
Often used attributively, as in 'backup generator' or 'backup plan'.
To make a duplicate copy of data as a precaution against loss; less commonly, to provide support or reinforcement.
"Remember to back up your documents before updating the operating system."
As a verb this is normally written as two words: 'back up'.
Regular plural; common in computing when referring to multiple saved copies.
"She keeps weekly backups of her entire photo library."
The phrase 'call for backup' comes straight from police radio slang — and today most of us 'call for backup' from a cloud server rather than a colleague.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of backup
Backup is an English compound formed from the older words 'back' (from Old English bæc, related to Old Norse bak) and 'up.' It arose in the twentieth century, first in military and police contexts referring to supporting forces, before becoming central vocabulary of computing as data storage developed. Its many 'back-' relatives — backdrop, backlog, background — all share the same root element.
How backup is actually used
In computing contexts, 'backup' is standard technical vocabulary; elsewhere it often carries a connotation of prudence or preparedness. As a verb, it is usually written 'back up' as two words.
Easily confused with backup
'Backup' is a noun meaning a reserve copy or support, while 'back up' is a two-word verb phrase meaning to move backward or to make such a copy.