مَجْرُوْرٌ

A noun moves from its natural nominative state to a genitive state مَجْرُوْرٌ in two instances 1) when it is preceded by a preposition الْمَسْبُوْقُ بِحَرْفِ جَرٍّ or 2) when it is in the possessive case الْمُضَافُ إِلَيْهِ

Genitive case / عَلَامَةُ الْجَرِّ كَسْرَةٌ

Noun / الْاِسْمُ

How to recognize Jarr جَرٌّ:

Singular nouns will end with (i) اِ or (in) اٍ sound

Pair / dual nouns will end with (ay) اَيْ or (ayni) اَيْنِ sound

Plural nouns will end with (ee) اِيْ or (eena) اِيْنَ sound

Plural feminine nouns will end with (aati) آتِ or (aatin) آتٍ sound

Broken plural nouns will end with (i) اِ or (in) اٍ sound same as singular, making them difficult to distinguish from singular