This is the 2327th most frequent Russian word.
младший
Younger; junior.
Here, 'младший' is used to describe a sibling in relation to their younger age compared to another person.
Моя младшая сестра любит читать книги.
My younger sister loves reading books.
In this sentence, 'младший' is used to describe the speaker's relative age in comparison to others in a group.
Я младший в нашей группе студентов.
I am the youngest in our group of students.
The usage of 'младший' here denotes a lower or initial rank in a professional context.