Lewis & Short

Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.

ărithmētĭca, ae, and -ē, ēs, f., = ἀριθμητική (sc. τέχνη), arithmetic, the science of numbers: arithmetica, Sen. Ep. 88; arithmetice, Vitr. 1, 1, and Plin. 35, 10, 36, § 76.

ărithmētĭcus, a, um, adj., = ἀριθμητικός, of or pertaining to arithmetic, arithmetical: ratio, Vitr. 10, 16.
Subst.: ărithmētĭca, ōrum, n., arithmetic: in arithmeticis satis exercitatus, Cic. Att. 14, 12 fin.