The five characteristics of lifeforms were organization (a distinct form and appearance), irritability (the ability to respond to external stimuli), metabolism (the ability to convert energy to stay alive), reproduction (the ability to create new lifeforms), and adaptation (the ability to change as their environments change).

A species given the sapient definition is considered able to reason and understand abstract metaphorical concepts and ideas, make and use tools, and communicate with written or spoken language. Species that did not reason at all and survived via their natural instincts, were classified as non-sapient

The predominant form of sapient life in the galaxy was carbon-based lifeforms. However, other forms of sentient life did exist, such as silicon-based or energy-based lifeforms. Reports from remote parts of the galaxy even mentioned giant clouds of interstellar gas which had evolved a form of intelligence based on internal force-fields.

The study of sapient species