The number of a noun is important to know because some words in the sentence change depending on if a noun is singular or plural. Notice how adjectives, verbs, and pronouns change depending on noun number.
uhanē harī gaḍḍī chalāī sī
He/she drove a green car
uhanē harīā(n) gaḍḍīā(n) chalāīā(n) san
He/she drove two green cars
harī (green) and chalāī (drove) are used for the first sentence because gaḍḍī (cars) is singular whereas harīā(n) (green) and chalāīā(n) (drove) are used for the second sentence because gaḍḍīā(n) (car) is plural
mērā bēṭā roj khēḍadā hae
My son plays everyday
mērē bēṭē roj khēḍadē han
My sons play everyday
mērā (my) and khēḍadā (play) are used for the first sentence because bēṭā (son) is singular whereas mērē (my) and khēḍadē (play) are used for the second sentence because bēṭē (sons) is plural
ikk siāṇī janānī bhāshaṇ dē rahī sī
A wise woman was giving a speech
do siāṇīā(n) janānīā(n) bhāshaṇ dē rahīā(n) san
Two wise women were giving a speech
siāṇī (wise) and dē rahī (giving) are used for the first sentence because janānī (woman) is singular whereas siāṇīā(n) (wise) and dē rahīā(n) (giving) are used for the second sentence because janānīā(n) (women) is plural