DictionaryspareExtra or in reserve
adjective / noun / verb

spare

SPAIR/sper/

Available beyond immediate requirements.

The vehicle carries a spare wheel on its rear door.

A parked compact off-road vehicle has two rear wheels supporting it and an additional matching wheel secured upright to the outside of its closed rear door, visibly ready as a spare.
Etymology

Old English sparian included “use sparingly.” The adjective spare derives from, or shares a root with, the verb: something held back from use remains available when an extra need arises.

In context

Akshon12:38
asked some of his animator friends to help out in their spare time as well
How A Tiny Studio Embarrassed The Gaming Industry

More examples

  • I keep a spare in case this key breaks.
  • Can you spare a few minutes to help me?
  • We spare no expense on safety equipment.

Forms

spare · spares · spared · sparing

Similar words

extra
Extra emphasizes additional quantity rather than readiness for replacement.
backup
Backup specifically replaces or supports something if it fails.