rational

Capable of reasoning.

Logically sound; not self-contradictory or otherwise absurd.

Healthy or balanced intellectually; exhibiting reasonableness.

Comprising, or expressible as, a ratio

Of a number, capable of being expressed as the ratio of two integers.

Of an algebraic expression in indeterminates, or more generally a function: capable of being expressed as the ratio of two polynomials.

Behaving according to some partial order of preferences.

Of a point on an algebraic variety over a field: whose coordinates belong to the field in question (in contrast to those points of the variety which are only defined over the algebraic closure of the base field).

Of a function between varieties: acting as a morphism on an open subset of its domain.

Of a variety: (informally) geometrically simple almost everywhere; (formally) birationally equivalent to projective space

(no longer used) synonymous replacement for "condensed" in condensed formula.

A rational number: a number that can be expressed as the quotient of two integers.

(historical) The breastplate worn by Israelite high priests.