sorry for asking question that might be considered as stupid but I keep on thinking for the definition of living beings Life, term used to summarize the activities characteristic of all organisms—ranging from such primitive forms as cyanobacteria (formerly known as blue-green algae) to plants and animals. These activities fall into two major categories: reproduction and metabolism. Microsoft ® Encarta ® 2006. © 1993-2005 Microsoft Corporation. All rights reserved. Using this definition, a fire would "reproduce" and "metabolise" The other major activity of living organisms is metabolism, the physical and chemical processes by which energy from the outside world is used in such activities as reproduction (including growth), Microsoft ® Encarta ® 2006. © 1993-2005 Microsoft Corporation. All rights reserved. I am unable to satisfy my self in nearly all definition of living beings that I ever find. The closest one is given by a friend of mine: "anything that can be killed" But I am sure there are better ones.