Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
1. sĭon, ii, n., = σίον, water-parsley: Sium latifolium, Linn.; Plin. 26, 8, 56, § 88; 22, 22, 41, § 84.
2. Sīon, ōnis (or indecl.), m., f., or n., a hill of Jerusalem, and, by meton., Jerusalem, Prud. Ham. 459; Vulg. Matt. 21, 5: facta est deserta Sion, id. Isa. 64, 10.