This is the 6764th most frequent Polish word.
ernestyna
"Ernestyna" is a Polish feminine given name, equivalent to "Ernestine" in English.
Here the word 'Ernestyna' is utilized as a proper noun, specifically as a personal name referring to an individual.
Ernestyna jest moją najlepszą przyjaciółką.
Ernestyna is my best friend.
In this sentence, 'Ernestyną' is the instrumental form of the proper noun 'Ernestyna', indicating involvement or communication with the person named.
Rozmawiałem z Ernestyną wczoraj wieczorem.
I spoke with Ernestyna last evening.
Here 'Ernestyna' is used in its nominative form, serving as the subject of the sentence referring to the person in question.