This is the 3781st most frequent Polish word.
najmłodsza
"Najmłodsza" means "the youngest" in English.
The word 'najmłodsza' is used here as a superlative adjective describing the feminine subject 'she', indicating that she is the youngest individual in the group.
Ona jest najmłodsza w naszej grupie.
She is the youngest in our group.
Here, 'najmłodszą' serves as a predicative adjective in the instrumental case, modifying the feminine noun 'chairperson' to describe her as being the youngest person to have held this role.
Została wybrana najmłodszą przewodniczącą tego klubu.
She was elected as the youngest chairperson of this club.
In this sentence, 'najmłodsza' is an attributive adjective, used before the noun 'sister' to specify that she is the youngest sibling among them.