1 (wiktionary) 2 (vi.wikipedia) 3 (en.wikipedia) 4 (glosbe)

CORE WORDS

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BODMER10 (1.u) GENERAL reason (power of thought) racio (pensopovo) förnuft fornuft vernuft (n) die Vernunft — — — die Vernunft
BODMER10 4. ADJECTIVES reasonable (rational) racia (racia) förnuftig fornuftig verstandig vernünftig — — — vernünftig

BRIT6000 reason,intellect Vernunft ragione raison razón
BRIT6000 reasonable,rational vernünftig ragionevole raisonnable razonable
BRIT6000 sane vernünftig sano di mente raisonnable sano de mente
BRIT6000 sense,intelligence Vernunft giudizio bon sens entendimiento
BRIT6000 sensible,reasonable vernünftig ragionevole sensé sensato
BRIT6000 unreasonable,unreasoning unvernünftig irragionevole déraidonnable irrazonable

Expert Personality and human behaviour (un)vernünftig + (ir)rational, (un)reasonable + Good/poor judgment A
Expert Personality and human behaviour Vernünftigkeit + good sense + Good/poor judgment A

It is contrary to reason .	Nó trái với lẽ phải.
A man of reason could answer the question .	Một người đàn ông của lý trí có thể trả lời câu hỏi.
The mother tried to reason with her son .	Người mẹ cố gắng giải thích với con trai mình.