Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
pĭrum, i, n., a pear, Cato, R. R. 7; Varr. R. R. 1, 59, 3; Col. 5, 10, 18; Plin. 15, 15, 16, § 53; Cloat. ap. Macr. S. 2, 15; Plaut. Poen. 2, 38; Juv. 11, 73: insitiva decerpens pira, Hor. Epod. 2, 19; id. Ep. 1, 7, 14; Verg. G. 2, 88.
pĭrus, i, f., a pear-tree: insere nunc, Meliboee, piros, Verg. E. 1, 74; Plin. 16, 24, 38, § 90; 16, 26, 46, § 109; 16, 25, 42, § 103: felix arbor, Macr. S. 3, 20, 2.