noun, plural car·di·nal·i·ties. Mathematics.
- (of a set) the cardinal number indicating the number of elements in the set.
- maths the property of possessing a cardinal number
- maths logic (of a class) the cardinal number associated with the given class. Two classes have the same cardinality if they can be put in one-to-one correspondence
1520s, “condition of being a cardinal,” from cardinal (n.) + -ity. Mathematical sense is from 1935 (see cardinal (adj.)).