#polish cases

Nominative (mianownik)- case of a noun which generally marks the subject of a verb or the predicate noun or predicate adjective, as opposed to its object or other verb argument.

Genitive (dopełniacz)- case that marks a noun as modifying another noun. It often marks a noun as being the possessor of another noun. It can indicate various relationships other than possession: certain verbs may take arguments in the genitive case and it may have adverbial uses.

Dative (celownik)- case used to indicate, among other uses, the noun to which something is given.

Accusative (biernik)- case used to mark the direct object of a transitive verb.

Instrumental (narzędnik)- case used to indicate that a noun is the instrument or means by or with which the subject achieves or accomplishes an action. The noun may be either a physical object or an abstract concept.

Locative (miejscownik)- case which indicates a location. Corresponds vaguely to the English prepositions “in”, “on”, “at”, and “by”. The locative case belongs to the general local cases together with the lative and separative cases.

This is kind of complicated to explain so I found this explanation, hope it helps-

For each gender there are forms for the Nominative, Genitive, Dative, Accusative, Instrumental, Locative, and Vocative cases (you don’t really need to know the names, just what they are) - seven cases in all, in both singular and plural. In general,

the Nominative case is used to express the SUBJECT of a sentence

the Dative to express the INDIRECT OBJECT (to or for whom something is done)

the Accusative the DIRECT OBJECT (the item perceived by or acted on by the subject)

The Instrumental expresses the MEANS BY WHICH something is done (for example, ride by train, write with a pen)

The Genitive expresses POSSESSION and, in general, most meanings of of, for example husband of my sister, top of the mountain, end of the film, and so on.

 The Locative is used with certain prepositions, especially prepositions expressing the simple locational senses of of, in, at, on.

Yes, you are right that if its a number from 5-10 or ending with a 5 or 0, you say piw. this happens with most things i believe that you have to change the endings for certain numbers, like an example is:

2 lamps- dwie lampy

5 lamps- pięć lamp

or

2 commercials- dwie reklamy

5 commercials- pięć reklam

or

2 houses- dwa domy

5 houses- pięć domów

With Polish all of these cases, which some of you probably know about (the przypadki), it gets very complicated sometimes. There are some patterns but they don't hold true for everything. It's a very irregular language because of these cases and that's why many people even deem polish as one of the hardest languages in the world. But don't worry, even if you were to use the wrong ending people would still understand you, what you'd be saying would just be awkward.