411 REFERENCE · Wiktionary
NOT operator
Reference material by Wiktionary contributors. This retains its source identity and is not 411 news reporting.
English
Noun
en mathematics logic An operation on logical values that changes true to false, and false to true.
Usage notes
The symbols ¬, !, ~, ˈ and Ā have all been used for the NOT operator in various contexts.
Wikipedia has an article on negation.