Benjamin Leonard D'Ooge, Latin for beginners (1911)
“ THE THIRD DECLENSION • Ī-STEMS 241. To decline a noun of the third declension correctly we must know whether or not it is an i-stem. Nouns with i-stems are 1. Masculines and feminines: a. Nouns in -ēs and -īs with the same number of syllables in the genitive as in the nominative. Thus caedēs, caedis, is an i-stem, but mīles, mīlitis, is a consonant stem. ”
