Formal logic

La regla de inferencia is the rule of inference, and la regla is a word where the two languages divide the work along different lines. Spanish uses it for the rule and for the thing you draw a line with: una regla de treinta centímetros is a ruler. English gives the measuring stick and the monarch one name — a ruler rules — where Spanish keeps el gobernante well away from la regla. And Spanish has a third sense that surprises the reader who meets it in a pharmacy: tener la regla is to have one's period. Same word, three jobs, and only one of them is the one this list means.