Rational

Rational

Adjective · /ˈræʃənl/ · based on reason and logic rather than emotion or instinct

Definition

Rational describes thinking, behaviour, or decisions that are based on clear logical reasoning rather than on feeling, impulse, or habit. A rational decision is one you could defend with evidence and argument. A rational person considers consequences before acting. In mathematics, a rational number is one that can be expressed as a fraction of two integers — the opposite of irrational, which cannot. Both mathematical and everyday senses share the same core: capable of being calculated, reasoned about, and accounted for.

Origin

From Latin rationalis, derived from ratio — reason, reckoning, calculation. The suffix -alis means pertaining to. Rational entered Middle English via Old French in the 14th century and has been used in philosophical, mathematical, and everyday contexts ever since. Its opposite, irrational, appeared almost simultaneously — a sign that the concept of rational thinking was immediately understood as something not everyone displayed.