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redundancy

ri-DUN-duhn-see /rɪˈdʌndənsi/

nounC1GREGMATCAT

technicalprofessionalacademic

The inclusion of extra, duplicate components or systems that are not strictly necessary to functioning, but serve as a backup in case of primary failure.

In daily language, 'redundancy' is negative (meaning useless repetition or job layoffs). In engineering and universal design, however, 'redundancy' is highly positive, representing a critical safety net (e.g., dual braking systems).

The story behind the word. The word originally described water overflowing its banks, like waves washing over a shore. By the 17th century, it came to describe an overflow of words or concepts, and in the 20th century, engineers adopted it to describe an 'overflow' of safety systems that keep a machine running.

Word relationships

backup: Backup is a general term for a replacement, whereas redundancy implies an active, parallel system ready to take over instantly.
duplication: Duplication can imply unnecessary or wasteful copying, whereas redundancy is a calculated safety measure.

singularity: Singularity implies a single point of failure where no backup system exists.

Commonly confused with

superfluity: Superfluity is an excess of something that is useless or wasteful; redundancy is a deliberate excess designed to prevent system failure.

Word family

redundant (adjective): Not strictly needed, or acting as a duplicate backup.
redundantly (adverb): In a manner that provides a backup or duplicate function.

Collocations

system redundancy
built-in redundancy
redundancy plan
data redundancy

Example sentences

"The spacecraft was designed with triple system redundancy, ensuring that if the primary flight computer failed, two backup computers could still pilot the vessel." An aerospace engineering safety brief.
"Adding text descriptions to audio files provides a helpful redundancy that benefits both deaf users and people in noisy environments." A lecture on accessible web design.

Memory hook

Think of 'redundancy' as 're-done-dancy'. The system is 're-done' (duplicated) so that if one partner falls, the dance continues. A backup that saves the day.

When not to use

Do not use 'redundancy' to describe a mistake or a waste of resources in engineering. In technical fields, it is a deliberate, planned safety feature.

Fun facts

Commercial airplanes are designed with massive hydraulic and electrical redundancies; they can fly and land safely even if multiple engines and control systems fail completely.