This is a sentence that's been deleted but still appears until Duolingo sorts some things out with their system. However there is a valid point that all named oceans in Welsh use the word for sea 'Môr' so that the Atlantic ocean is 'Y Môr Iwerydd', the Pacific ocean is 'Y Môr Tawel' etc.
Thanks for that. I did once ask why, if all the large bodies of water are 'Y Mor' where do the Welsh use ' Y cefnfor'. ? Someone said that you could use it as in 'an ocean view' but, if the water you are looking at is 'Y mor', surely what you have is a sea view? I've just never understood why one needs a word that describes something else. I don't explain my quandry very well, maybe that's because I'm so confused.
Perhaps you could think about y Môr Du (the Black Sea) as a 'sea' in comparison with y Môr Iwerydd or just yr Iwerydd (the 'Atlantic Ocean' or 'the Atlantic') which is definitely an 'ocean' cefnfor.
*y Môr xxx' is just a naming convention, not a definition of size. It is just another example of there not being a one-to-one correspondence between English and Welsh words and usages.
It's not a matter of size. My question is more on the lines of, 'If nothing is called an ocean, why did you invent the word?' I've given up hoping for an answer: Your "just another example of there not being a one-to-one correspondence between English and Welsh words and usages." will just have to satisfy me.