rational
Meaning
Based on reason or logic, not emotions or feelings.
Able to think clearly and make decisions based on reason.
(Mathematics) Expressible as a ratio of whole numbers.
Structure
Usage
There must be a rational explanation for what happened.
In a crisis, it's important to stay calm and rational.
The number 0.75 is a rational number because it can be written as 3/4.
Etymology
The word 'rational' originates from the Latin 'rationalis', meaning "of or belonging to reason," which itself derives from 'ratio' (genitive 'rationis'), signifying "reckoning, calculation, reason." The Latin 'ratio' stems from the past participle stem 'ratus' of the verb 'reri', "to reckon, think." This etymological journey reflects a core progression from the concrete act of mathematical calculation to the abstract faculty of logical reasoning. Thus, the modern meanings—from logical thought to expressible fractions—are directly tied to this ancient concept of measured reckoning.
Analysis
'ratio' is from Latin 'ratio' (reckoning, reason, calculation). '-nal' is an English adjective-forming suffix, a variant of '-al', from Latin '-alis'.