a young person (especially a young man or boy)
"The coach praised the youth for his incredible speed on the field."
the time of life between childhood and maturity
"The local sports league offers special training programs for anyone in their youth to help them develop skills before turning professional."
early maturity; the state of being young or immature or inexperienced
"His youth made him overlook several important details during the project review."
the freshness and vitality characteristic of a young person
"Her dance was full of such infectious youth that everyone in the crowd felt like they were only twenty again."
The quality or state of being young.
"The park is filled with the vibrant energy and boundless hope that comes from youth."
In plain English: Youth is the time when you are young, full of energy, and not yet an adult.
"The school organized sports activities for local youth after classes ended."
Usage: Use "youth" to refer specifically to people in their younger years rather than the abstract concept of youthfulness, which is better expressed as "the quality of being young." When referring to a group of young people collectively, it often takes an article (e.g., "in my youth") or functions as a mass noun without pluralization.
The word youth comes from Old English ġeoguþ, which originally meant the state of being young. It traveled into Modern English through Middle English while retaining its core meaning related to young people.