A telephone number not listed in the directory.

(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.

plural of atomic number

plural of decimal number

(algebra, field theory) algebraic number field

(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 number line

(mathematics) A line that graphically represents the real numbers as a series of points whose distance from an origin is proportional to their value

(physics) A Reynolds number at which the flow of a fluid changes from laminar to turbulent.

plural of Betti number