Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Ā̆prīlis, is [qs. contr. from aperilis, from aperio; cf. Varr. L. L. 6, 33, p. 86 Müll.; Cincius ap. Macr. S. 1, 12; Serv. ad Verg. G. 1, 43] (orig. adj.; sc. mensis), m., the month of April (as the month in which the earth opens and softens): Sex ubi luces Aprilis habebit, Ov. F. 4, 901.
With mensis expressed: mense Aprili, Cic. Phil. 2, 39, 100: Qui dies mensem Veneris marinae Findit Aprilem, Hor. C. 4, 11, 15.
Adj., of or pertaining to April: Nonarum Aprilium, Cic. Fam. 3, 11, 8; 1, 9, 8: Datis mane a. d. Id. April. Scriptis litteris, id. ad Brut. 2, 4, 1: Apriles Idus, Ov. F. 4, 621.