ABSTRACT
This chapter presents various perspectives on defining life. It provides an overview of the most common approaches to defining life is given, accompanied by a selection of definitions of life that illustrate these approaches. The chapter describes advantages and disadvantages of minimal versus expanded definitions of life. One of the key goals of astrobiology is to define life, which is important not only for understanding the origin and evolution of life on Earth but also for the search for extraterrestrial life. New molecular biology tools, such as the Clustered Regularly Interspaced Short Palindromic Repeats gene-editing method, provide additional ways to tinker with the building blocks of life. Some definitions of life are expanded dictionary definitions of life, in which the additional description is added for the use by specialists. Autopoiesis is a concept proposed and developed by Maturana and Varela as the sole requirement for life.
