Collective noun: When referring to a group of young people, "youth" acts as a collective noun.
* Example: "The youth of today are more connected than ever before." (Here, "youth" represents a group.)
Singular noun: When referring to the quality or period of being young, "youth" acts as a singular noun.
* Example: "Her youth was full of adventure." (Here, "youth" refers to the state of being young, not a group.)
Therefore, whether "youth" is a collective noun depends on how it is used in a sentence.