The most common numbers in Latin, as in English, are the cardinal numbers. Second are the ordinals, which are ranking numbers.
Cardinal Numbers
Cardinal numbers in Latin are indeclinable adjectives, except for ūnus (one), duo (two), trēs (three), and mīlle (thousand).
| Case | Duō (Two) | Trēs (Three) | Mīlle (Thousand) / Mīlia (Thousands) | ||||
|---|---|---|---|---|---|---|---|
| Masculine | Feminine | Masculine | Feminine | Neuter | Singular | Plural | |
| Nominative | duō | duae | trēs | trēs | tria | mīlle | mīlia |
| Genitive | duōrum | duārum | trium | trium | trium | mīlle | mīlium |
| Dative | duōbus | duābus | tribus | tribus | tribus | mīlle | mīlibus |
| Accusative | duōs | duās | trēs | trēs | tria | mīlle | mīlia |
| Ablative | duōbus | duābus | tribus | tribus | tribus | mīlle | mīlibus |
The cardinals indicating the hundreds place, from 200 through to 900 are declined like plural adjectives of the first and second declension (Latin Declensions). e.g. ducentī, ducentae, ducenta. Mīlle is a indeclinable adjective in the singular but a i-stem neuter noun of the third declension. (i-stem noun notes)
Ordinal Numerals
Thankfully, each of the ordinals are regular first/second declension adjectives. They do still have to be memorized.