In the US, we call our garden-variety, everyday limes Persian limes, but here's a conundrum: there is no word in Arabic for limes, even though most of what you get in Egypt when you ask for lemons are not lemons, or even Persian limes, You get what seem to be Key limes! I actually have seen 'lemons' once or twice in the fancy market here in Cairo, but all that is usually available are the little Key limes. I have to say that this puzzles me...
We get those small Egyptian limes in Dubai as well imported and available at the grocery store. They are probably not key limes, but some other type of lime. Where a lime ends and a lemon begins must exist on some taxonomical continuum, but linguistically there is not always a difference.
In many parts of the world there are only limes OR only lemons available as the indigenous fruit, not both. That is why there are not two separate words distinguishing between lime and lemon. It is the same in Hindi/Urdu (nimbu) and other Indo-Iranian languages, as well as in Vietnamese (chanh).
The words lime and lemon themselves are from an Arabic lexical adoption into English, from the original Arabic limoon (which was itself an adoption from the Farsi), which is a term that broadly covers the semantic category of citrus fruit that we in English further split into lemon and lime.
I googled up a fun article about the history of the lime/lemon word in the English language: http://www.billcasselman.com/fruit_na...
Thanks, luckyfatima. Very informative! The Egyptian limes are really good. At the club across the street where my son trains they make a "lemonade" with them by throwing the whole thing in a blender with sugar and ice. Naturally, it's very green, but it is also tart and very tasty. The skins of the limes are so thin that they easily get whirred by the blender.