an accumulation caused by clogging or a stoppage
"a traffic backup on the main street"
"he discovered a backup in the toilet"
someone who takes the place of another (as when things get dangerous or difficult)
"the star had a stand-in for dangerous scenes"
"we need extra employees for summer fill-ins"
a musical part (vocal or instrumental) that supports or provides background for other musical parts
"The choir added soft harmonies to serve as backup for the lead singer's powerful solo."
(computer science) a copy of a file or directory on a separate storage device
"he made a backup in case the original was accidentally damaged or erased"
the act of providing approval and support
"his vigorous backing of the conservatives got him in trouble with progressives"
A reserve or substitute.
"When our main speaker got sick, his backup stepped in to lead the meeting without any hesitation."
In plain English: A backup is an extra copy of something you keep so you don't lose it if the original gets damaged or deleted.
"I need to create a backup of my important files just in case my computer crashes."
Usage: Use backup as a noun to refer to a person or item kept on hand as a substitute in case the primary one fails or becomes unavailable. Do not use it to describe an action of backing up data, which should remain a verb phrase.
Misspelling of back up.
"That's just a misspelling of "back up," so please fix it in your document."
In plain English: To backup means to move backward, usually to get out of a tight spot or create more space behind you.
"Please backup your important files before the computer crashes."
Usage: Use "backup" only as a noun to refer to a spare copy or support system; do not use it as a verb. To describe the action of creating a duplicate or supporting something, you must write "back up" with a space between the words.
Standby, reserve or extra.
"We kept a backup generator running just in case the main power failed during the storm."
In plain English: A backup is something extra you keep ready just in case your main plan or item fails.
"I keep a backup copy of my important files on an external hard drive."
Usage: Use backup as an adjective to describe something kept on hand as a reserve or substitute when the primary option fails. It functions directly before a noun, such as in "backup plan" or "backup generator," to indicate readiness for use.
The word backup comes directly from the phrase back up, which originally meant to move something backward before shifting into its modern sense of a reserve copy or support system. It entered English as a straightforward combination of two existing words rather than evolving from a more complex linguistic root.