Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
căpĭtellum, i, n. dim. [caput, capitulum] (perh. first post-class., for in Plin. 24, 19, 113, § 173, and 36, 23, 56, § 178, the MSS. and edd. vary between capitellum and capitulum; not in use in the time of Varro; v. Varr. L. L. 8, § 79 Müll.).