Betti number

Meaning

Noun

• Any of a sequence of numbers, denoted b_n, which characterise a given topological space K by giving, for each dimension, the number of holes in K of said dimension; the rank of the nth homology group, H_n, of K.

Origin

• A calque of French nombre de Betti, coined in 1892 by Henri Poincaré; named after Italian mathematician Enrico Betti in recognition of an 1871 paper.