A non-zero member of a partially ordered set that has only zero below it (assuming that the poset has a least element, its "zero").
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.
In logical atomism, a fundamental fact that cannot be further broken down.
The smallest medieval unit of time, equal to fifteen ninety-fourths of a second.
An age group division in hockey for nine- to eleven-year-olds.
An element of a set that is not itself a set; an urelement.
A mote of dust in a sunbeam.
A hypothetical particle posited by Greek philosophers as an ultimate and indivisible component of matter.
The smallest, indivisible constituent part or unit of something.
A very small amount; a whit.
An individual number or symbol, as opposed to a list; a scalar value.
A non-empty lower set (of a partially ordered set) which is closed under binary suprema (a.k.a. joins).
A subsemigroup with the property that if any semigroup element outside of it is added to any one of its members, the result must lie outside of it.
A subring closed under multiplication by its containing ring.
A collection of sets, considered small or negligible, such that every subset of each member and the union of any two members are also members of the collection.
A perfect standard of beauty, intellect etc., or a standard of excellence to aim at.
A Lie subalgebra (subspace that is closed under the Lie bracket) 𝖍 of a given Lie algebra 𝖌 such that the Lie bracket [𝖌,𝖍] is a subset of 𝖍.
Not actually present, but considered as present when limits at infinity are included.
Optimal; being the best possibility.
Existing only in the mind; conceptual, imaginary.
Pertaining to ideas, or to a given idea.
Perfect, flawless, having no defects.
Teaching or relating to the doctrine of idealism.