Blume --> plural?

(a)  

Nouns which end in -ung, -schaft, -heit, -or -keit are (a)  

Nouns which end in -ung, -schaft, -heit, -or -keit add (a)   to form the plural

Leute, Eltern and Ferien are always (a)  

If you see Schwester(-n) in the dictionary, how would you then work out two sisters

(a)  

If you see Zimmer(-) in the dictionary, how would you then work out four rooms

(a)  

A plural noun in the dative case, must always end in (a)  

DATIVE:

my friends = meine Freunde

with my friends = (a)  

DATIVE:

his brothers = seine Brüder

from/of his brothers = (a)