Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
longĭtĭa (longĭcĭa), ae, f. [longus], length (late Lat.), Auct. de Limit. p. 271; Goes. Veg. Vet. 6, 2, 2 (Schneid. longitudo).