Some oranges, especially the ones you find in Asia or at Asian fruit stands, can be completely ripe and still completely green. The ones sold in US stores are almost all sour and unripe if they are green (almost always but not always). Different regions in the world 'know about' different citrus fruit (there seem to be a lot of overlap and a lot of non-overlap with fruit), so your mileage may vary. Reddit claims this is because of the temperatures: https://www.reddit.com/r/VietNam/comments/16ca895/why_are_th... It's fun to go to fruit stands when traveling and try the fruits you don't recognize! Lots of fruits are very different if you travel to countries where they can grow them natively, and there are a lot of tropical fruits that aren't exported. Lots of the English words for fruits are re-used so you can be eating something totally unrecognized and it's a "tree cherry" or something.
For example, what they call a lime in a lot of countries (for example Calamansi) would be called a tiny orange in North America (we don't have that fruit here). What we call a lime they wouldn't recognize, but if they saw/tasted it they might think it's a green lemon or something.
> For example, what they call a lime in a lot of countries (for example Calamansi) would be called a tiny orange in North America (we don't have that fruit here).
Calamansi limes are grown in California and usually called Calamondin limes. They're typically anywhere from orange to yellow/green when grown here.
> What we call a lime they wouldn't recognize, but if they saw/tasted it they might think it's a green lemon or something.
What country doesn't have what we call a lime? The Key lime, like the Calamansi is is native to the Philippines and available everywhere the Calamansi is. Persian limes are exported nearly everywhere.
Lots of languages don't differentiate between lemons and limes though.
A Key Lime is only vaguely a lime (they call it a Dayap and I don't think they would consider it a lime at all), that's why we call them 'Key Lime' instead of just lime. I'm putting a fine point on it, but I think when we say 'Lime' we mean something like a Persian Lime. You don't make Persian Lime pie!
As far as I know in the Philippines they don't have a common word to describe a Persian lime, and I never saw one in a store there.
Persian limes are just a cross between key limes and lemons. Before Persian limes were popularized in the 20th century, key limes were just called "limes" in the US (and still are in cocktail recipes and latin markets).