What term describes the entire period of human existence from conception to death?

The term that describes the entire period of human existence from conception to death is "Lifespan." This concept encompasses all stages of life, including prenatal development, infancy, childhood, adolescence, adulthood, and old age, highlighting the continuous journey of growth and change that every individual experiences throughout their lifetime.

The notion of lifespan is integral to understanding human development, as it incorporates the biological, psychological, and social changes that occur over time. By focusing on the lifespan, we can appreciate how experiences and environments influence individuals at various stages and how they adapt from conception to the end of life.

Other terms like "Stages of Development" refer specifically to distinct periods within the lifespan, while "Developmental Milestones" signify key achievements or skills that individuals are expected to reach at particular ages. "Critical Periods" denotes specific time frames during which certain developmental processes are particularly crucial, but these do not encompass the entirety of human existence.