1. [noun] (now historical) The smallest medieval unit of time, equal to fifteen ninety-fourths of a second. [from 10th c.]
2. [noun] (history of science) A hypothetical particle posited by Greek philosophers as an ultimate and indivisible component of matter. [from 15th c.]
3. [noun] (physics) (chemistry) The smallest possible amount of matter which still retains its identity as a chemical element, now known to consist of a nucleus surrounded by electrons. [from 16th c.]
4. [noun] A mote of dust in a sunbeam. [from 16th c.]
5. [noun] The smallest, indivisible constituent part or unit of something. (Now generally interpreted as a figurative use of the physics sense, above.) [from 17th c.]
6. [noun] A very small amount (of something immaterial); a whit. [from 17th c.]
7. [noun] (mathematics) A non-zero member of a Boolean algebra that is not a union of any other elements. [from 20th c.]
8. [noun] (computing) (programming) (Lisp) An individual number or symbol, as opposed to a list. A scalar value.
9. [noun] (physics and chemistry) the smallest component of an element having the chemical properties of the element.
10. [noun] (nontechnical usage) a tiny piece of anything.
