(topology, algebraic topology) Any of a sequence of numbers, denoted bₙ, which characterise a given topological space K by giving, for each dimension, the number of holes in K of said dimension; (formally) the rank of the nth homology group, Hₙ, of K.

plural of Betti number

plural of ordinal number

plural of atomic number

(US) A nine-digit number issued to citizens, permanent residents, and temporary (working) residents under section 205(c)(2) of the Social Security Act, codified as 42 U.S.C. § 405(c)(2). The number is issued to an individual by the Social Security Administration. Its primary purpose is to track individuals for taxation purposes. Abbreviated as SSN. In recent years the SSN has become a de facto national identification number.

(genetics) The number of copies of a gene or plasmid within a cell's genome. / (library science) The identification number assigned to a specific copy of a work.

plural of decimal number

(algebra, field theory) algebraic number field

Several. / Several of.

(mathematics) By means of, or in terms of, number theory.