Polski — plural-only nouns
Some Polish nouns exist only in the plural (pluralia tantum): drzwi "door", spodnie "trousers", nożyczki "scissors", okulary "glasses", wakacje "holidays", urodziny "birthday". They have no singular form, even when they refer to a single object.
How it works
Since there is no singular, everything agrees in the plural: the verb, adjectives and numerals. You say te nowe spodnie "these new trousers", drzwi są otwarte "the door is open", and to count them you use collective numerals — dwoje drzwi "two doors", troje nożyczek "three (pairs of) scissors".
Declension (drzwi)
| Case | drzwi (door) | okulary (glasses) |
|---|---|---|
| Nominative | drzwi | okulary |
| Genitive | drzwi | okularów |
| Dative | drzwiom | okularom |
| Accusative | drzwi | okulary |
| Instrumental | drzwiami | okularami |
| Locative | drzwiach | okularach |
Good to know
The genitive is the trap: some end in -i/-y (drzwi, spodni), others take -ów (okularów) — you must learn each. Also, do not translate the English singular literally: "a birthday" is still plural urodziny (moje urodziny są w maju "my birthday is in May"), and to say "one door" use jedne drzwi, not jeden.