Similar words
millar
millar is more formal, used for counting large quantities, like "millares de personas," thousands of people; mil is the everyday number word.
Similar in other languages
French
mille
mille is the French word for the same thing — both mean "thousand."
Practice
1 What does mil mean?
thousand
2 Fill the gap: Cuesta ___ euros.
Full sentence: Cuesta mil euros. (It costs a thousand euros.)
3 Which fingerprint chart matches mil?
mil: neutral register, core frequency, general domain, neutral connotation.