Redundant means no longer needed. The thing is still there, but nothing depends on it any more: the fax machine in the corner, the second sentence that says what the first one already said.
In Britain the word carries a hard workplace meaning. To be made redundant is to lose your job because the job itself has been cut, not because you were bad at it: two hundred staff were made redundant, and the noun is redundancy, with redundancy pay to soften it. Americans say laid off, and leave redundant to the other senses. Engineers turn the word right over: a redundant system is a spare one, duplicated on purpose so that a failure changes nothing, and redundancy there is a virtue. In writing, redundant marks the words doing no work — free gift, past history, each one saying the same thing twice.
1adjectiveredundantNo longer needed or useful.
“Once the new bridge opened, the ferry was redundant.”
synonyms: unnecessary, superfluous
2adjectiverepeatingRepeating what has already been said, and so adding nothing.
“Cut the second paragraph, because it is redundant.”
3adjectiveemployedNo longer employed, because the job has been cut.
“Half the office was made redundant in the spring.”
4adjectiveduplicatedDuplicated on purpose, as a backup in case one part fails.
“The aircraft has redundant hydraulic systems for exactly this reason.”
Also accepted in games: unnecessary
Redundant comes from Latin redundāns, from redundō, to overflow. Inside it is unda, a wave, the same wave that swells through undulate and abundant. Something redundant has spilled over the rim: there is more of it than the container has any use for.
Proto-Indo-European
*wed-
Latin
redundāns
English, today
redundant
Built from
From Latin redundāns, present participle of redundō (“to overflow, redound”), from red- (“again, back”) + undō (“to surge, flood”), from unda (“a wave”).
Etymology from Wiktionary, CC BY-SA