rationalis

Rationalis is a Latin adjective meaning rational, reasonable, or pertaining to reason. It is formed from ratio, meaning reason, and the suffix -alis, which conveys a characteristic. As a Latin adjective, rationalis agrees with the noun it modifies in gender and number, and it is used across prose, philosophy, theology, and legal writing to describe things connected with reason or rational faculties. In some contexts, rationalis can also function as a substantive referring to the rational faculty or the rational mind.

In classical and medieval philosophy, rationalis often occurs in discussions of the human soul and intellect. The phrase anima rationalis contrasted with anima sensitiva or other forms of life, highlighting the distinctive role of reason in humans. The concept of rationalis cognition or rationalis deliberatio appears in scholastic treatises that seek to explain how reason governs assent and judgment. In theological writings, rationalis operation is described in relation to free will and moral agency.

In modern scholarship, rationalis continues to appear in translations of Latin works and in the study of Latin grammar. It is less common as an independent term in everyday English, where 'rational' is preferred, but it remains a standard lexical item in Latin dictionaries and lexicographic descriptions of philosophical and legal Latin phrases. The word also forms part of compound terms in Latin phrases such as rationalis natura or rationalis intellectus, reflecting its broad application to reasoning-related concepts.