Some very interesting facts on 2nd declension masculines in -us.

Gap-fill exercise

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Latin masculine nouns of the second declension have a nominative singular ending in -, and a singular ending in -i. Note that the singular ending is the same as the and vocative plural. There are two other cases with identical endings in the second declension. These are the : they have the same ending - in the singular, and the same ending - in the . The genitive plural ending - is the only one consisting on two syllables, and is always accented on the -o-. The accusative ends in -um in the and in - in the plural. Masculine nouns of the second declension are the only ones that have a special ending for the vocative case (only in the , however), and this is -.