This is the 14994th most frequent Russian word.
подросток
Adolescent; teenager.
Here, 'подросток' is used as the subject to indicate a person in the stage of transition between childhood and adulthood.
Подросток часто сталкивается с трудностями переходного возраста.
A teenager often encounters challenges of the transitional age.
In this sentence, 'подросток' is used in the singular genitive case to denote 'of a teenager' in possessive relation.
Родители иногда не понимают чувства и переживания подростка.
Parents sometimes don't understand the feelings and experiences of the teenager.
Here, 'подростков' is used in the plural genitive case to indicate a group of individuals in their teenager years.