# De Morgan's laws

### or De Mor·gan's law

[dih mawr-guh nz lawz or dih mawr-guh nz law]

### noun

(used with a plural verb) Logic. two laws, one stating that the denial of the conjunction of a class of propositions is equivalent to the disjunction of the denials of a proposition, and the other stating that the denial of the disjunction of a class of propositions is equivalent to the conjunction of the denials of the propositions.

(used with a singular verb) Mathematics.

- the theorem of set theory that the complement of the union of two sets is equal to the intersection of the complements of the sets.
- the theorem of set theory that the complement of the intersection of two sets is equal to the union of the complements of the sets.

## Origin of De Morgan's laws

First recorded in 1915–20; named after A. De Morgan

Dictionary.com Unabridged
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

## De Morgan's laws

### pl n

## Word Origin for De Morgan's laws

named after Augustus De Morgan (1806–71), British mathematician

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012