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Latin Grammar I, Lesson 15. On the Accusative Singular of the Third Declension

In this short lesson, we learn of the formation of the accusative case in the third declension of the Latin language.


1. Accusativus Latinus in EM, ut sermonem; buris tamen cucumis, pelvis, securis, sitis, tussis, vis in IM exeunt, burim, etc. Clavis, febris, navis frequentius in EM quam in IM; at puppis, restisis, turris usitatius in IM quam in EM.

Translation: (The) Latin accusative ends in EM, as sermonem; buris, nevertheless, cucumis, pelvis, ravis, securis, sitis, tussis, vis ends in IM, burim, etc. Clavis, febris, navis ends more frequently in EM than in IM; but puppis, restisis, turris is more usual in IM than in EM.

Nouns that end in EM

In this lesson, we learn about two different endings for nouns of the third declension in the accusative case. The most common accusative ending in the third declension is -EM. We see this in the noun sermo, whose accusative form is sermonem.

Let’s note a few things about third declension nouns.

When we first learned about the “declension” of nouns, in lesson 03 of Latin Grammar I, we learned that the declension to which a noun belongs is identified by the genitive singular ending. Thus, for the noun sermo, the genitive singular form is sermonis. The ending -IS identifies it as a third declension noun.

If we remove that genitive singular ending, we have the “stem” of the noun. Therefore, the stem of the noun sermo is SERMON-. It is to this stem that the accusative endings in this lesson are added.

Back to the lesson…

Nouns that end in IM

While -EM is the most common accusative ending in the third declension, -IM is found in some third declension nouns. These nouns are listed as: buris (plow), cucumis (cucumber), pelvis (basin), securis (ax), sitis (thirst), tussis (cough), vis (strength). Their accusative case forms are: burim, cucumerim, pelvim, securim, sitim, tussim, vim.

Nouns that end in EM or IM

In the second half of the rule, we learn about nouns that are found to end in EM or IM in Latin writing. These divide into two groups: those that more often end in -EM, and those that more often end in -IM.

I. The nouns clavis (key), febris (fever), navis (ship) end more frequently in EM than in IM; thus, their accusative forms are more usually clavem, febrem, navem rather than clavim, febrim, and navim.

II. The nouns puppis (ship), restisis (pause), turris (tower) more usually end in IM than in EM; thus, their accusative forms are more usually puppim, resistim, turrim, rather than puppem, resistem, turrem.

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