Citron
A source of confusion is that "citron" or similar words in French (and other languages), and English are false friends, as they refer to the lemon. Indeed, into the 16th century, the English name "citron" included the lemon and perhaps the lime as well.
Lime (fruit)
A lime (from French "lime", from Arabic "līma", from Persian "līmū", "lemon") is a hybrid citrus fruit, which is typically round, green in color, in diameter, and contains acidic juice vesicles.