One who rations.

plural of rationing

(now rare) Rationally, reasonably.

rationing

(mathematics) A number that can be expressed as the ratio of two integers.

plural of rational number

(mathematics) The set of numbers that can be expressed as a ratio of integers, often denoted with the bold letter Q, or the blackboard bold letter ℚ.

(mathematics, complex analysis, algebraic geometry) Any function expressible as the quotient of two (coprime) polynomials (and which thus has poles at a finite, discrete set of points which are the roots of the denominator).

an advocate of rational egoism

(philosophy) The doctrine that it is rational to act in one's own self-interest. / (philosophy) A theory espoused by Ayn Rand, combining this doctrine with ethical egoism.