rationem

Rationem is the accusative singular of ratio, a Latin noun of the third declension. In classical Latin, ratio carries multiple related meanings, including reason, calculation, reckoning, account, method, and plan. The sense "reason" covers logical justification or cause; "calculation" or "reckoning" refers to numerical computation or accounting; "account" or "consideration" appears in phrases such as reddere rationem (to render an account or provide an explanation). The term is often found in philosophical, legal, and mathematical texts to denote justification, proportional relations, or systematic method.

In grammar, ratio is feminine; other forms align with 3rd-declension endings: gen. rationis, dat. rationi, acc. rationem, abl. ratione; plural rationes, rationum, rationibus, rationes, rationibus.

Etymology: ratio yields the source of many English terms. In philosophy and science, ratio occurs in Latin as "reason" or "method"; in English, derivative words include ratio (as a mathematical proportion), rational, rationality, rationale, rationalize.

Usage examples: classical authors use rationem in phrases like "reddere rationem" or "pro ratione" to indicate justification or reason; medieval and early modern writers employ ratio to discuss method or logical demonstration.

In modern contexts, rationem is chiefly encountered in the study of Latin language and literature. It remains a key term for understanding how ancient texts express justification, calculation, and method, and it underpins the English vocabulary connected to reason and proportion.