Polish language is a inflected language which mean that the words are changing their form and endings depending of their position and function in the sentence: the verbs depends on the person (I, you, he, she, it, we , you plural and they) as well as on the tense it is used and the nouns are declined (changed) depending on the grammatical case that the verb or the pronoun is followed with.
Mam dom (I have a house), dom is in Accusative as for the verb to have in statement goes with Accusative.
Nie mam domu (I do not have a house), domu is in Genetive, as for the negation in Polish is followed with Genetive case.
GRAMMATICAL CASES (PRZYPADKI)
There are seven cases in Polish, the last one, Vocative is rarely used:
1. MIANOWNIK (KTO? CO?) NOMINATIVE, FOLLOWED BY THE QUESTIONS WHO? WHAT?
2. DOPEŁNIACZ (KOGO? CZEGO?) GENITIVE
3. CELOWNIK (KOMU? CZEMU?)
4. BIERNIK (KOGO? CO?) ACCUSATIVE
5. NARZĘDNIK (KOMU? CZEMU?) INSTRUMENTAL
6. MIEJSCOWNIK (O KIM? O CZYM?) LOCATIVE/PREPOSITIONAL CASE
7. WOŁACZ (O!) VOCATIVE
BELOW THE EXAMPLES OF DELINATION:
NOS (NOSE, masculine) MAMA (MUM, feminine) JAJKO (EGG, neuter)
What is a grammatical case?
Brief description of CASE FORMATION in Polish go
Essential Guide to Polish