The Collaborative International Dictionary of English v.0.48:
Numerosity \Nu`mer*os"i*ty\, n. [L. numerositas.] 1. The state of being numerous; numerousness. [Obs.] [1913 Webster] 2. Rhythm; harmony; flow. [Obs.] [1913 Webster] The numerosity of the sentence pleased the ear. --S. Parr. [1913 Webster]WordNet (r) 3.0 (2006):
numerosity n 1: a large number [syn: numerousness, numerosity, multiplicity]