There are common irregularities that occur during declension of nouns. These irregularities occur in the last syllable of the noun's stem. You should apply these irregularities from the perspective of a noun in Singular Nominative Case form. The most common irregularities are:

	Transition I	Transition II
mobile e	removing e	inserting e
mobile ie	removing ie	inserting ie
ó ↔ o exchange	exchanging ó ➜ o	exchanging o ➜ ó
ą ↔ ę exchange	exchanging ą ➜ ę	exchanging ę ➜ ą

Look at the squares in the first column of the table above. Throughout the articles on my website you can find these squares next to nouns. This is a convention for marking nouns that have irregularities during declension. You can always hover over the square to see which transition it is.

As shown in the table above, each irregularity has two possible transitions. Which transition to use depends on whether you are adding or removing an ending:

use Transition I when you are adding an ending to a noun. If a noun has an irregularity, then this irregularity will be applied to all forms of the noun where an ending is added.
use Transition II when you are removing an ending from a noun. It happens when you are adding the
∅
no ending
ending. In practice ending removal happens only in Plural Genitive Case for feminine and neuter nouns, so this transition is used only in these two places.

You must learn by heart whether a noun has an irregularity and what kind of irregularity it has. At the end of the article I added some general tips that may help you guess if a noun has an irregularity. Remember that these are not golden rules and many nouns don't follow them. It's always best to check the declension table for a given noun when you learn it for the first time.

Examples

Below you can see 8 example declinations with common irregularities. One for each irregularity. We start with each noun in its dictionary form (Singular Nominative Case).

budynek(building)

budynek

noun

owi

budynek

take stem

remove

owi

attach

budynk

owi

budynkowi

Dative Singular

notatka(note)

notatka

noun

∅

notatk

take stem

insert

∅

no ending

notat

notatek

Genitive Plural

pies(dog)

pies

noun

pies

take stem

remove

attach

psa

Genitive Singular

okno(window)

okno

noun

∅

okn

take stem

insert

∅

no ending

okien

Genitive Plural

samochód(car)

samochód

noun

samochód

take stem

ó ➜ o

replace

attach

samoch

samochody

Nominative Plural

prośba(request)

prośba

noun

∅

prośb

take stem

o ➜ ó

replace

∅

no ending

śb

próśb

Genitive Plural

mąż(husband)

mąż

noun

mąż

take stem

ą ➜ ę

replace

attach

mężem

Instrumental Singular

ręka(hand)

ręka

noun

∅

ręk

take stem

ę ➜ ą

replace

∅

no ending

rąk

Genitive Plural

The tables below present full declinations of the nouns from above's examples.

budynek - building

Case	Singular	Plural
Nominative	budynek	budynki
Genitive	budynku	budynków
Dative	budynkowi	budynkom
Accusative	budynek	budynki
Instrumental	budynkiem	budynkami
Locative	budynku	budynkach
Vocative	budynku	budynki

notatka - note

Case	Singular	Plural
Nominative	notatka	notatki
Genitive	notatki	notatek
Dative	notatce	notatkom
Accusative	notatkę	notatki
Instrumental	notatką	notatkami
Locative	notatce	notatkach
Vocative	notatko	notatki

pies - dog

Case	Singular	Plural
Nominative	pies	psy
Genitive	psa	psów
Dative	psu	psom
Accusative	psa	psy
Instrumental	psem	psami
Locative	psie	psach
Vocative	psie	psy

okno - window

Case	Singular	Plural
Nominative	okno	okna
Genitive	okna	okien
Dative	oknu	oknom
Accusative	okno	okna
Instrumental	oknem	oknami
Locative	oknie	oknach
Vocative	okno	okna

samochód - car

Case	Singular	Plural
Nominative	samochód	samochody
Genitive	samochodu	samochodów
Dative	samochodowi	samochodom
Accusative	samochód	samochody
Instrumental	samochodem	samochodami
Locative	samochodzie	samochodach
Vocative	samochodzie	samochody

prośba - request

Case	Singular	Plural
Nominative	prośba	prośby
Genitive	prośby	próśb
Dative	prośbie	prośbom
Accusative	prośbę	prośby
Instrumental	prośbą	prośbami
Locative	prośbie	prośbach
Vocative	prośbo	prośby

mąż - husband

Case	Singular	Plural
Nominative	mąż	mężowie
Genitive	męża	mężów
Dative	mężowi	mężom
Accusative	męża	mężów
Instrumental	mężem	mężami
Locative	mężu	mężach
Vocative	mężu	mężowie

ręka - hand

Case	Singular	Plural
Nominative	ręka	ręce
Genitive	ręki	rąk
Dative	ręce	rękom
Accusative	rękę	ręce
Instrumental	ręką	rękami
Locative	ręce	rękach
Vocative	ręko	ręce

How do I know when to apply an irregularity?

Unfortunately, there is no golden rule for this. When you learn a new noun, you should check the declension table for it and memorize if it has an irregularity. However, there are some patterns that can help you guess if a noun has an irregularity:

When a masculine or feminine noun ends in e/ie/ó/ą + a consonant in the Singular Nominative Case and you are adding an ending, there is a chance you must apply an irregularity:
budynek budynku
pies psa
stół stołu
mąż męża
krew krwi
wieś wsią
gałąź gałęzie
sól soli
When a feminine noun loses its -a vowel in the Plural Genitive Case and has o/ę in the last syllable, there is a chance you must apply an irregularity:
siostra sióstr
ręka rąk
przygoda przygód
When a feminine noun loses its -a vowel in the Plural Genitive Case and after that it has two or more consonants at the end, there is a chance you must apply an irregularity:
szklanka szklanek
wojna wojen
pralka pralek
cegła cegieł
When a neuter noun loses its -o/e vowel in the Plural Genitive Case and has o/ę in the last syllable, there is a chance you must apply an irregularity:
morze mórz
święto świąt
słowo słów
dobro dóbr
When a neuter noun loses its -o vowel in the Plural Genitive Case and after that it has two or more consonants at the end, there is a chance you must apply an irregularity:
okno okien
łóżko łóżek
wiadro wiader
źródło źródeł
piętro pięter
jabłko jabłek
biodro bioder

Noun Declension - Summary of Endings

Noun Declension - Softening

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Cases - Noun Declension

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After reading this book you will be able to decline any noun in the Polish language. This book also contains exercises with answers, which will help you practice what you learn.

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Noun Declension - Common Irregularities

	Transition I	Transition II
mobile e	removing e	inserting e
mobile ie	removing ie	inserting ie
ó ↔ o exchange	exchanging ó ➜ o	exchanging o ➜ ó
ą ↔ ę exchange	exchanging ą ➜ ę	exchanging ę ➜ ą

As shown in the table above, each irregularity has two possible transitions. Which transition to use depends on whether you are adding or removing an ending:

use Transition I when you are adding an ending to a noun. If a noun has an irregularity, then this irregularity will be applied to all forms of the noun where an ending is added.
use Transition II when you are removing an ending from a noun. It happens when you are adding the
∅
no ending
ending. In practice ending removal happens only in Plural Genitive Case for feminine and neuter nouns, so this transition is used only in these two places.

Examples

Below you can see 8 example declinations with common irregularities. One for each irregularity. We start with each noun in its dictionary form (Singular Nominative Case).

budynek(building)

budynek

noun

owi

budynek

take stem

remove

owi

attach

budynk

owi

budynkowi

Dative Singular

notatka(note)

notatka

noun

∅

notatk

take stem

insert

∅

no ending

notat

notatek

Genitive Plural

pies(dog)

pies

noun

pies

take stem

remove

attach

psa

Genitive Singular

okno(window)

okno

noun

∅

okn

take stem

insert

∅

no ending

okien

Genitive Plural

samochód(car)

samochód

noun

samochód

take stem

ó ➜ o

replace

attach

samoch

samochody

Nominative Plural

prośba(request)

prośba

noun

∅

prośb

take stem

o ➜ ó

replace

∅

no ending

śb

próśb

Genitive Plural

mąż(husband)

mąż

noun

mąż

take stem

ą ➜ ę

replace

attach

mężem

Instrumental Singular

ręka(hand)

ręka

noun

∅

ręk

take stem

ę ➜ ą

replace

∅

no ending

rąk

Genitive Plural

The tables below present full declinations of the nouns from above's examples.

budynek - building

Case	Singular	Plural
Nominative	budynek	budynki
Genitive	budynku	budynków
Dative	budynkowi	budynkom
Accusative	budynek	budynki
Instrumental	budynkiem	budynkami
Locative	budynku	budynkach
Vocative	budynku	budynki

notatka - note

Case	Singular	Plural
Nominative	notatka	notatki
Genitive	notatki	notatek
Dative	notatce	notatkom
Accusative	notatkę	notatki
Instrumental	notatką	notatkami
Locative	notatce	notatkach
Vocative	notatko	notatki

pies - dog

Case	Singular	Plural
Nominative	pies	psy
Genitive	psa	psów
Dative	psu	psom
Accusative	psa	psy
Instrumental	psem	psami
Locative	psie	psach
Vocative	psie	psy

okno - window

Case	Singular	Plural
Nominative	okno	okna
Genitive	okna	okien
Dative	oknu	oknom
Accusative	okno	okna
Instrumental	oknem	oknami
Locative	oknie	oknach
Vocative	okno	okna

samochód - car

Case	Singular	Plural
Nominative	samochód	samochody
Genitive	samochodu	samochodów
Dative	samochodowi	samochodom
Accusative	samochód	samochody
Instrumental	samochodem	samochodami
Locative	samochodzie	samochodach
Vocative	samochodzie	samochody

prośba - request

Case	Singular	Plural
Nominative	prośba	prośby
Genitive	prośby	próśb
Dative	prośbie	prośbom
Accusative	prośbę	prośby
Instrumental	prośbą	prośbami
Locative	prośbie	prośbach
Vocative	prośbo	prośby

mąż - husband

Case	Singular	Plural
Nominative	mąż	mężowie
Genitive	męża	mężów
Dative	mężowi	mężom
Accusative	męża	mężów
Instrumental	mężem	mężami
Locative	mężu	mężach
Vocative	mężu	mężowie

ręka - hand

Case	Singular	Plural
Nominative	ręka	ręce
Genitive	ręki	rąk
Dative	ręce	rękom
Accusative	rękę	ręce
Instrumental	ręką	rękami
Locative	ręce	rękach
Vocative	ręko	ręce

How do I know when to apply an irregularity?

When a masculine or feminine noun ends in e/ie/ó/ą + a consonant in the Singular Nominative Case and you are adding an ending, there is a chance you must apply an irregularity:
budynek budynku
pies psa
stół stołu
mąż męża
krew krwi
wieś wsią
gałąź gałęzie
sól soli
When a feminine noun loses its -a vowel in the Plural Genitive Case and has o/ę in the last syllable, there is a chance you must apply an irregularity:
siostra sióstr
ręka rąk
przygoda przygód
When a feminine noun loses its -a vowel in the Plural Genitive Case and after that it has two or more consonants at the end, there is a chance you must apply an irregularity:
szklanka szklanek
wojna wojen
pralka pralek
cegła cegieł
When a neuter noun loses its -o/e vowel in the Plural Genitive Case and has o/ę in the last syllable, there is a chance you must apply an irregularity:
morze mórz
święto świąt
słowo słów
dobro dóbr
When a neuter noun loses its -o vowel in the Plural Genitive Case and after that it has two or more consonants at the end, there is a chance you must apply an irregularity:
okno okien
łóżko łóżek
wiadro wiader
źródło źródeł
piętro pięter
jabłko jabłek
biodro bioder

Noun Declension - Summary of Endings

Noun Declension - Softening

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Cases - Noun Declension

After reading this book you will be able to decline any noun in the Polish language. This book also contains exercises with answers, which will help you practice what you learn.

Paperback

E-book

End of Advertisement

budynek	budynku
pies	psa
stół	stołu
mąż	męża
krew	krwi
wieś	wsią
gałąź	gałęzie
sól	soli

siostra	sióstr
ręka	rąk
przygoda	przygód

szklanka	szklanek
wojna	wojen
pralka	pralek
cegła	cegieł

morze	mórz
święto	świąt
słowo	słów
dobro	dóbr

okno	okien
łóżko	łóżek
wiadro	wiader
źródło	źródeł
piętro	pięter
jabłko	jabłek
biodro	bioder