This is the 2077th most frequent Polish word.
młodszy
"Junior" or "younger."
The word 'młodszy' is used here to compare the age of two individuals.
Mój brat jest młodszy ode mnie.
My brother is younger than me.
In this sentence, 'młodszy' changes its form to 'młodsza' to agree with the feminine subject, emphasizing relative age inside the family.
Marysia jest młodsza siostrą w naszej rodzinie.
Marysia is the younger sister in our family.
Here, 'młodszy' is used in a metaphorical sense to describe a feeling or perception of youthfulness.