accusative
accusativus
The case of the direct object: whom? what? — what the action reaches directly. With prepositions such as “in” and “ad” it marks direction.
in the texts
Panem nostrum quotidiánum da nobis
give what — bread.
I beseech whom — Mary.
“in” with the accusative — direction: into temptation.
“ad” with the accusative — to the Lord.