Genitive

The genitive case is the Latin grammatical case of possession that marks a noun as being the possessor of another noun, for example in English "Popillia's book" or in "board of directors", but it can also indicate various relationships other than possessions.

The genitive is the only grammatical case in Latin which is different in each of the five declensions, so the genitive case serves to distinguish the single declensions from each other.

Here are the basic and very general rules for making a genitive in singular:

• If a word ends in "-us" or "-um", then the genitive ends in "-i". "Tullius" becomes "Tullii"; "forum" will be "fori".
• If a word ends in "-a", then the genitive ends in "-ae". "Livia" becomes "Liviae".
• If a word ends in "-o", then the genitive ends in "-onis". "Cicero" becomes "Ciceronis".
• Many other words change their ending to "-is" whose rules are more difficult and are not detailed here. Here are some just for example:

"Audens" in dative becomes "Audentis",

"Venus" in dative is "Veneris",

"homo" in dative is "hominis",

"consul" in dative is "consulis", and so on.

• Some common nouns ending in "-us" change their ending to long "-ús" in genitive, for example:

"Senatus" in dative is "Senatús",

"exercitus" in dative is "exercitús",

Usage in practice

Avarage Nova Roman citizen has to use genitive in some expressions like "pater patriae", "scriba censoris" but it is also useful when one connects people to offices, or want to entitle a message in Latin, or especially when addressing magistrates' assistants.