"The teacher has students."
Translation:Magistra discipulas habet.
I typed Magister discipulos habet. which is also marked correct.
Am I correct in that -os is masc. pl. accusative and -as is fem. pl. acc. ?
Yes (with exceptions),
-os is the second declension 'masculine' accusative plural (there are some second declension feminine nouns out there that will have this ending in the accusative plural).
-as is the first declension accusative plural (there are some masculine first declensions out there like nauta, which would use nautas in the accusative plural).
There are also second declensions that have the '-er' ending in the nominative. These are slightly different than the '-us' second declensions for a few of the cases.
First declension are mostly feminine nouns but a few masculine nouns exist (nauta, poeta). Second declension nouns with a nominative that end in '-us' are mostly masculine, some feminine (humus, domus when treated as a second declension). Second declension nouns with a nominative that ends in '-um' are neuter.
|Case||First||Second (-us)||Second (-um)|