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An overbar on a set name, meaning everything outside it.
Also known as: Set complement, Overbar complement, Not-set bar
A bar drawn over a set name denotes its complement: everything in the surrounding universe that the set does not contain. The notation only works when the universe is agreed, and a superscript c or a prime is used for the same idea, so three notations coexist for one operation.
Denotes the complement of a set — all the elements of the agreed universal set that are not in it.
Contexts: Mathematics
Depends on a universal set being fixed by context; without one the complement of a set is not defined.
Contexts: Mathematics
Competes with a superscript c and with a prime for the same meaning, and the same overbar means closure in topology and conjugation on complex numbers.
Contexts: Mathematics
A horizontal line ruled across the top of a letter, spanning its full width and not touching it.