Tortoise and turtle are the same in Welsh? (Tortoise is living on the land, turtle lives in the water if I am right)
Duo accepts both.
If you need to be more exact:
Crwban - tortoise/turtle
Crwban dŵr - turtle/terrapin
Crwban y môr or môr-grwban - sea turtle
Crwban dŵr croyw or terapin - terrapin
Wikipedia says, "Differences exist in usage of the common terms turtle, tortoise, and terrapin, depending on the variety of English being used; usage is inconsistent and contradictory. These terms are common names and do not reflect precise biological or taxonomic distinctions."
So it should perhaps not be surprising that many other languages use one name for all chelonians - possibly distinguishing, if necessary, "land chelonians" from "water chelonians" by using a descriptive adjective or noun.
Eh, we learnt in the school that it is very strict... this is how you can trust them :D Even in my language (HU) there is an originally definite difference between land and water chelonians ("teknős" vs "teknőc") but nobody cares now—even I don't know which is what :D ) (I think that "teknős" is the water dwelling one. I should ask one of them, perhaps they're knowing...)
Another distinction English makes that not everyone else does is the one between "apes" and "monkeys".
Multi lingual comedian Eddie Izzard has a short piece about this- French calls them all singe
Much as we distinguish between ape and monkey we still call the macaques of Gibraltar Barbary Apes.
According to multilingual comedian Eddie Izzard, the French have one word for monkeys and apes.
I've also been told that the Chinese have one word for sheep and goats. (I'm presuming in Mandarin at least)