Polski — Fleeting e
In many Polish nouns the vowel e in the last syllable appears in some case forms and disappears in others: pies but psa, dzień but dnia. This alternation is called the fleeting (or mobile) e.
How it works
The e usually shows up in the nominative singular (the dictionary form) and drops out once an ending is added: pies → psa, marzec → marca, sen → snu, dzień → dnia, cukier → cukru. The rest of the paradigm keeps the shortened stem (psu, psem, psie), so once the e is gone in the genitive it stays gone.
Examples
| Nominative | Genitive | Meaning |
|---|---|---|
| pies | psa | dog |
| marzec | marca | March |
| sen | snu | dream, sleep |
| dzień | dnia | day |
| cukier | cukru | sugar |
| ogień | ognia | fire |
Good to know
Not every final e is fleeting: in serce → serca or słońce → słońca the e belongs to the ending, not the stem. And some nouns gain an e in the genitive plural instead: matka → matek, okno → okien. When in doubt, check the genitive form in a dictionary — that is where the alternation shows.