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.
Citropten
Citropten is a natural organic compound with the molecular formula CHO. It is found in the essential oils of citrus such as lime, lemon, and bergamot.