One of the simplest or essential parts or principles of which anything consists, or upon which the constitution or fundamental powers of anything are based.
User Defined Definitions
"an abstract part of something"
"an artifact that is one of the individual parts of which a composite entity is made up; especially a part that can be separated from or attached to a system"
"the most favorable environment for a plant or animal"
"one of four substances thought in ancient and medieval cosmology to constitute the physical universe"
"the situation in which you are happiest and most effective"
"a straight line that generates a cylinder or cone"