Youth is generally the time of life between childhood and adulthood (maturity). Definitions of the specific age range that constitutes youth vary. An individual's actual maturity may not correspond to their chronological age, as immature individuals can exist at all ages. Youth is also defined as "the appearance, freshness, vigor, spirit, etc., characteristic of one who is young". Youth is a term used for people of both sexes, male and female, of a young age. Usage Around the world, the terms "youth", "adolescent", "teenager", "kid", and "young person" are interchanged, often meaning the same thing, occasionally differentiated. Youth generally refers to a time of life that is neither childhood nor adulthood, but rather somewhere in-between. Youth also identifies a particular mindset of attitude, as in "He is very youthful". The term youth is also related to being young. The term also refers to individuals between the ages of 16-24. "This world demands the qualities of youth: not a time of life but a state of mind, a temper of the will, a quality of imagination, a predominance of courage over timidity, of the appetite for adventure over the life of ease." - Robert Kennedy Youth is an alternative word to the scientifically-oriented adolescent and the common terms of teen and teenager. Another common title for youth is young person or young people. Population aged under 15 years in 2005 Youth is the stage of constructing the Self-concept. The self-concept of youth is influenced by several variables such as peers, lifestyle, gender and culture. It is this time of a person's life which they make choices which will affect their future.  August 12th was declared International Youth Day by the United Nations. Self-concept (also called self-construction, self-identity or self-perspective) is a multi-dimensional construct that refers to an individual's perception of "self" in r lation to any number of characteristics, such as academics (and nonacademics), gender roles and sexuality, racial identity, and many others. Each of these characteristics is a research domain (i.e. Academic Self-Concept) within the larger spectrum of self-concept although no characteristics exist in isolation as one’s self-concept is a collection of beliefs about oneself. While closely related with self-concept clarity (which "refers to the extent to which self-knowledge is clearly and confidently defined, internally consistent, and temporally stable"), it presupposes but is distinguishable from self-awareness, which is simply an individual's awareness of their self. It is also more general than self-esteem, which is a function of the purely evaluative element of the self-concept. The self-concept is an internal model which comprises self-assessments. Features assessed include but are not limited to: personality, skills and abilities, occupation(s) and hobbies, physical characteristics, etc. For example, the statement "I am lazy" is a self-assessment that contributes to the self-concept. However, the statement "I am tired" would not be part of someone's self-concept, since being tired is a temporary state and a more objective judgment. A person's self-concept may change with time as reassessment occurs, which in extreme cases can lead to identity crises. Another model of self-concept contains three parts: self-esteem, stability, and self-efficacy. Self-esteem is the "evaluative" component—it is where one makes judgments about his or her self-worth. Stability refers to the organization and continuity of one's self-concept. Is it constantly in flux? Can singular, relatively trivial events drastically affect your self-esteem? The third element, self-efficacy, is best explained as self-confidence. It is specifically connected with one's abilities, unlike self-esteem.