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.
Citrus
In general, three "Citrus" ancestral species (pomelos, citrons, and papedas) synthesize relatively high quantities of furanocoumarins, whereas a fourth ancestral species (mandarins) is practically devoid of these compounds. Since the production of furanocoumarins in plants is believed to be heritable, the descendants of mandarins (such as sweet oranges, tangerines, and other small mandarin hybrids) are expected to have low quantities of furanocoumarins, whereas other hybrids (such as limes, grapefruit, and sour oranges) are expected to have relatively high quantities of these compounds.