Always Decline Using the Root
The root of a noun is found by removing the ending from the genetive singular. This is why the ablative singular form of words like magister is magistro and not magistero.
The accusative form of neuter nouns is always the same as its nominative form, no matter what declension.
Odds and Ends
- Nouns ending in -ius or -ium occurring before the reign of Augustus in 31 B.C. take the genitive (and locative) form of -ī instead of -iī.
- Nouns of the ŏ-stem second declension are either masculine or neuter, with a few exceptions (as always). For example, trees, towns and cities that end in -us are Feminine (e.g. Corinthus). Some names of countries, such as Aegyptus (Egypt), are also feminine.
- Some nouns of the second declension ŏ-stem will take the genitive plural form of -um instead of -ōrum. This is especially prevalent in words denoting money and measure, such as talentum (of talents).
- Nouns in this declension can sometimes be seen using the Greek style of inflection, especially before or during the time of Cicero. Nobody said you had to like it, but that’s the way long-lived languages behave.