Nouns are pretty simple. They belong to one of five declensions, which governs how they decline:
| . | First Declension | Second Declension | Third Declension | Fourth Declension | Fifth Declension |
|---|---|---|---|---|---|
| Nominative Singular | -a | -us/-um | -- | -us | res |
| Vocative Singular | -a | -e | -- | -us | res |
| Accusative Singular | -am | -um | -- | -um | rem |
| Genitive Singular | -ae | -i | -is | -us | rei |
| Dative Singular | -ae | -o | -e | -ui | rei |
| Ablative Singular | -a | -o | -e | -u/-o | re |
| Nominative Plural | -ae | -i | -es | -us | res |
| Vocative Plural | -ae | -i | -es | -us | res |
| Accusative Plural | -as | -os | -es | -us | res |
| Genitive Plural | -arum | -orum | -um | -uum | rerum |
| Dative Plural | -is | -is | -ibus | -ibus | rebus |
| Ablative Plural | -is | -is | -ibus | -ibus | rebus |
Note that the vocative is only different to the nominative in the second declension singular, and that plural datives and ablatives are the same. Also note that of fifth declension nouns, only res, and dies decline fully.
Nouns also have a gender. First declension nouns are always feminine. Second declension nouns are masculine if they have a "-us" ending in the nominative singular, and neuter if they have a "-um". Third and fourth declension nouns can be any gender. Fifth declension nouns are all masculine, except dies. Note that there are exceptions to these rules, particularly when referring to an obviously gendered thing e.g. agricola is masculine.
Also note that regardless of declension, neuter nouns always take an "-a" ending in the nominative and accusative plural, and are always the same in the nominative and accusative singular.
| First Person | Second Person | Third Person Masculine | Third Person Feminine | Third Person Neuter | |
|---|---|---|---|---|---|
| Nominative Singular | ego | tu | is | ea | id |
| Accusative Singular | me | te | eum | eam | id |
| Genitive Singular | mei | tui | eius | eius | eius |
| Dative Singular | mihi | tibi | ei | ei | ei |
| Ablative Singular | me | te | eo | ea | eo |
| Nominative Plural | nos | vos | ei | eae | ea |
| Accusative Plural | nos | vos | eos | eas | eos |
| Genitive Plural | nostrum | vostrum | eorum | earum | eorum |
| Dative Plural | nobis | vobis | eis | eis | eis |
| Ablative Plural | nobis | vobis | eis | eis | eis |
| . | Masculine | Feminine | Neuter |
|---|---|---|---|
| Nominative singular | hic | haec | hoc |
| Accusative singular | hunc | hanc | hoc |
| Genitive singular | huius | huius | huius |
| Dative singular | huic | huic | huic |
| Ablative singular | hoc | hac | hoc |
| Nominative Plural | hi | hae | haec |
| Accusative Plural | hos | has | haec |
| Genitive Plural | horum | harum | horum |
| Dative Plural | is | is | is |
| Ablative Plural | is | is | is |
| . | Masculine | Feminine | Neuter |
|---|---|---|---|
| Nominative singular | ille | illa | illud |
| Accusative singular | illum | illam | illud |
| Genitive singular | illius | illius | illius |
| Dative singular | illi | illi | illi |
| Ablative singular | illo | illa | illo |
| Nominative Plural | illi | illae | illa |
| Accusative Plural | illos | illas | illa |
| Genitive Plural | illorum | illarum | illorum |
| Dative Plural | illis | illis | illis |
| Ablative Plural | illis | illis | illis |