Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
crēbrĭtas, ātis, f. [creber], thickness, closeness, frequency: spissae venarum, Vitr. 2, 10, 2: caeli, id. 9, 8, 3: fluctuum, Sall. H. Fragm. ap. Serv. ad Verg. A. 1, 116 (3, 42 Dietsch): litterarum, Cic. Att. 13, 18 init.: crebritas et magnitudo officiorum, id. Fam. 3, 1, 1: sententiarum (with concinnitas), id. Brut. 95, 327.