- A substance composed of atoms of only one kind, of identical atomic (proton) number, that therefore cannot be decomposed into two or more elements and that can lose its chemical properties only by union with some other element or by a nuclear reaction changing the proton number.
- An indivisible structure or entity.
- A functional entity, frequently exogenous, within a bacterium, such as an extrachromosomal element.
[L. elementum, a rudiment, beginning]
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Examples: glitazone, GI cocktail, etc.