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 non-empty lower set (of a partially ordered set) which is closed under binary suprema (a.k.a. joins).
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.
Produced by alteration or deposition subsequent to the formation of the original rock mass.
Derived from a parent compound by replacement of two atoms of hydrogen by organic radicals
Developed by pressure or other causes.
Dependent or consequent upon another disease, or occurring in the second stage of a disease.
Related to secondary education, i.e. schooling between the ages of (approximately) 11 and 18.
Of less than primary importance.
Originating from a deputy or delegated person or body
Representing a reversion to an ancestral state.
Formed by mixing primary colors.
Next in order to the first or primary; of second place in origin, rank, etc.
Pertaining to the second joint of the wing of a bird.
Relating to the manufacture of goods from raw materials.
One who occupies a subordinate or auxiliary place; a delegate deputy.
A radar return generated by the response of an aircraft's transponder to an interrogation signal broadcast by a radar installation, containing additional encoded identification and situational data not available from a simple primary return.
The defensive backs.
An inductive coil or loop that is magnetically powered by a primary in a transformer or similar.
Any flight feather attached to the ulna (forearm) of a bird.
A satellite.
An act of issuing more stock by an already publicly traded corporation.
The second stage of a multistage thermonuclear weapon, which generates a fusion explosion when imploded as an indirect result of the fission explosion of the primary, and which, in a few extremely large weapons, itself implodes a fusion tertiary.
A secondary circle.
A secondary school.
Anything secondary or of lesser importance.