OBSERVATION: A description using sight, sound, smell, taste, and/or touch (your five senses).
OCTET RULE: An atom is stable when its valence electron shell is full, which is when it contains 8 electrons. The only exception to the octet rule is the first electron shell (H and He), which is complete with just 2 electrons.
OPTIMAL: The best
ORDER: A taxonomic ranking group of similar families.
ORGAN: A group of two or more types of tissue organized to perform complex activities within an organism. Example: heart, kidney, liver, lung
ORGANELLES: The membrane-bound structures found inside of a eukaryotic cell that perform specific functions. Examples: endoplasmic reticulum, lysosome, mitochondria
ORGANISM: Anything that can carry out the five characteristics of life
OSMOSIS: The movement of water from areas of high concentration to areas of low concentration without the use of energy. This is a form of passive transport.