WordReference Random House Unabridged Dictionary of American English © 2026
De Mor′gan's laws′,
- Philosophy[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.
- 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.
- named after A. De Morgan 1915–20