Definition of "rational" in English

adjective

1. Capable of reasoning.

   • Man is a rational creature.

2. Logically sound; not self-contradictory or otherwise absurd.

   • His statements were quite rational.
   • Prevention for the future is now almost universally allowed to be the only rational plea for the infliction of punishment; but this, when left to the arbitrary discretion of individuals, always has been found, and always will be found, to degenerate into the exercise of revenge for the past.

3. (of a person or personal characteristics) Healthy or balanced intellectually; exhibiting reasonableness.

   • rational conduct
   • Temperature 99.8 degrees. Pulse 104. She was quite conscious and rational at times, at others very noisy.

4. (mathematics, not comparable) Comprising, or expressible as, a ratio

5. (chemistry, obsolete) synonymous replacement for "condensed" in condensed formula.

noun

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

   • The quotient of two rationals is again a rational.

noun

1. (historical) The breastplate worn by Israelite high priests.