(countable) A young man; a male adolescent or young adult.
(countable) A young person.
(uncountable) The part of life following childhood; the period of existence preceding maturity or age; the whole early part of life, from childhood, or, sometimes, from infancy, to adulthood.
(uncountable) The quality or state of being young.
(uncountable, used with a plural or singular verb) Young persons, collectively.