Lifespan refers to the duration of time that an organism, such as a human, animal, or plant, is expected to live. It can vary significantly between different species, influenced by factors like genetics, environment, and lifestyle. For example, the average lifespan of a house cat is around 15 years, while some tortoises can live over 100 years. In scientific terms, lifespan can be measured in various ways, including maximum lifespan, which is the longest period an individual of a species has lived, and average lifespan, which is the mean age at death for a population. Understanding lifespan helps in fields like medicine and conservation.