Primary
Complement ○｜Definition｜1st｜20251119205401-00-⌔
Complement (set theory) - Wikipedia
Complement (set theory)
If A is the area colored red in this image…
… then the complement of A is everything else.
In set theory, the complement of a set A, often denoted by (or A ′),1 is the set of elements not in A.2
When all elements in the universe, i.e. all elements under consideration, are considered to be members of a given set U, the absolute complement of A is the set of elements in U that are not in A.
The relative complement of A with respect to a set B, also termed the set difference of B and A, written is the set of elements in B that are not in A.
Printed 2026-06-28.
(echo:: @ ᯤ)
Link to original Footnotes
“Complement and Set Difference”. web.mnstate.edu. Retrieved 2020-09-04. ↩
“Complement (set) Definition (Illustrated Mathematics Dictionary)”. www.mathsisfun.com. Retrieved 2020-09-04. ↩
Secondary
• • •