An organism is a living BEING that can exist independently. It can be a single-celled organism, such as an ameba, or a multi-celled organism, such as a human. The term 'organism' is derived from the Greek word 'organon, ' which means 'INSTRUMENT.' The acronym ECAD stands for 'Every Cell An Organism, ' which is a concept that emphasizes the importance of every cell in an organism. Lifeform is another term used to describe an organism, and it is often used to refer to complex organisms.