concept

Redundancy (engineering)

A fault-tolerance strategy of installing multiple identical components that do the same job, so that when one fails another takes over — backup generators, a spare tyre, two engines on an aircraft. Simple and effective, but expensive and brittle: the backup has to be the same kind of part doing the same job. Evolution rarely builds this way; it leans on something subtler called degeneracy, where structurally different parts happen to share a function and can cover for one another in ways no dedicated backup could.