Second Declension
There are a large number of nouns whose nominative singular can end with different endings such as -us, -er, -ir or -um. Their genitive singular case, though, ends always in -i.
These types of nouns have been grouped together and are said to belong to the second declension.
Nouns that end in -us are generally masculine except for some, not very many, that are feminine but use this masculine declension; for example the name of trees are always feminine, but the fruit of the trees are always masculine.
Nouns that end in -er and -ir are always masculine. Nouns that end in -um are always neutral.
Second Declension Paradigm of nouns ending in -us
| | Dominus, -i, m. & f. lord, squire, owner | | Cervus, -i, m. deer |
| Singular | Plural | | Singular | Plural |
Nom. | domin-us | domin-i | | cerv-us | cerv-i |
Gen. | domin-i | domin-orum | | cerv-i | cerv-orum |
Dat. | domin-o | domin-is | | cerv-o | cerv-is |
Acc. | domin-um | domin-os | | cerv-um | cerv-os |
Voc. | domin-e | domin-i | | cerv-us | cerv-i |
Abl. | domin-o | domin-is | | cerv-o | cerv-is |
N.B.: Feminine nouns that use the -us declension:
1- Some names of towns, islands and regions.
E.g.: Corinthus (Corynth - town), Cyprus (isle), Aegyptus (Egypt - region).
2- Names of trees.
E.g.: populus (poplar-tree), pirus (pear-tree), malus (apple-tree), prunus (plum-tree)
3- Specific names such as: humus (soil), domus (home), and a few others.
4- Some Greek names such as: apostrophus (apostrophe), dialectus (dialect), diphthongus (diphtong), and a few more.
Second Declension Paradigm of of nouns ending in -er
| | Puer, -i, m. boy | | Liber, -i, m. book |
| Singular | Plural | | Singular | Plural |
Nom. | puer | puer-i | | liber | libr-i |
Gen. | puer-i | puer-orum | | libr-i | libr-orum |
Dat. | puer-o | puer-is | | libr-o | libr-is |
Acc. | puer-um | puer-os | | libr-um | libr-os |
Voc. | puer | puer-i | | liber | libr-i |
Abl. | puer-o | puer-is | | libr-o | libr-is |
N.B.: Sone nouns with the nominative ending in -er, like liber above, will drop the "e" like in liber > libri > libro, librorum, etc.
Another such exception is magister > magistri > magistrorum, or aper (wild boar) etc.
Others, like socer (farher in law), gener (son in law), keep their "e" in all the cases like in puer. Words that keep the "e" are not many and the majority are declined as per liber, libri; a Latin dictionary will always show you the correct declension by quoting the genitive singular as: magister, -stri; liber, -bri.
Note: Lĭbĕr = book but Lībĕr = free (similar to the English sounds in ship and sheep); but the declension remains the same.