Leadership is the function of a leader. Leadership is also the period of time a leader spends.
According to Rath and Conchie (2009), "The most effective leaders know better than to try to be someone they are not" (pp. 79-85). This quote is only a sentence long, however it has a tremendously meaning. Leadership is the capability to conduct people with leaders that know better, rather than faking whom they are.
Rath, T. & Conchie, B. (2009). "Understanding why people follow." Strengths based leadership: Great leaders, teams, and why people follow. (pp. 79 - 85). New York: Gallup Press.