Le mot anglais pour rein est
kidney

Définition en anglais

rein
1. n-m. (anatomy) kidney
2. n-m. (in the plural) small of the back, waist

kidney	©
1. n. An organ in the body that filters the blood, producing urine.
2. n. This organ (of an animal) cooked as food.
3. n. (figuratively, dated) Constitution, temperament, nature, type, character, disposition. (usually used of people)
4. n. (obsolete, slang) A waiter.