my copy-paste from another thread:
"In the Soviet times Kiev was the standard as it is the transliteration of Russian name for this city: Киев. In Ukrainian it is Київ, so when we gained independency it was decided to introduce to standard usage the transliteration from Ukrainian instead of Russian: Kyiv. This is not an easy shift, so now basically both are used, but it is encouraged to use Kyiv and it is the name that's used by our authorities."
So Duolingo encourages you to use the transliteration from Ukrainian as you are learning a Ukrainian here :)
Ok, although Kiev has actually been the standard transliteration since 1820. Compare the following in Google's Ngram viewer for Kiev (attested starting in 1820)
vs. Kyiv (no use until 1950)
I get it, but I do suspect the original transliteration had more to do with making it pronounceable in English than anything else.
Oh, I just forgot to mention Russian Empire times :) Kyiv was part of Russian Empire since the end of XVIII century. Ukrainian haven't got any official status back then, so it was impossible for transliteration from Ukrainian to appear anywhere.
"From 1804 until the Russian Revolution, the Ukrainian language was banned from schools in the Russian Empire, of which the biggest part of Ukraine (Central, Eastern and Southern) was a part at the time"
I'm very sorry, only "Kyiv" is accepted according to the politics of the UkrDuo administrators.
Kiev is a common way to spell Київ in many languages.
My personal opinion is that it doesn't make sense to forbid it, since in many sources it is still officially spelled like that. Maybe their idea is that if we spell Київ differently, it will change people's attitude to our country. Which I think is not true. People can spell it any way they want, and perceive Ukraine as an independent country; and conversely they can be forced to spell "Kyiv" only and still treat Ukraine the way they want. It's not a subconscious effect on the mind or something.
Besides, what city is spelled and/or pronounced in a foreign language exactly the way it is in the original one? "Roma" is "Rome", "München" is Munich. Apart from that, "Kyiv" is confusing, it's unclear how to pronounce it. Since foreigners can't usually pronounce "и" anyway, and don't know that "y" means "и", spelling "Kiev" only makes sense. The short "i" in English sounds similar to "и", actually.
But... I'm not the one deciding. The admins decided it between themselves and removed "Kiev" from the accepted answers. Not everywhere though, it's still might be accepted in some exercises which is even worse because of the inconsistency. I removed on like this recently...