Lifespan refers to the duration of time that an organism is expected to live. It varies significantly across different species, influenced by factors such as genetics, environment, and lifestyle. For example, the average lifespan of a house cat is around 15 years, while tortoises can live for over 100 years. In humans, the average lifespan has increased over the past century due to advancements in medicine, nutrition, and public health. Currently, the global average lifespan is approximately 72 years, but it can differ based on geographic location, socioeconomic status, and access to healthcare.