As you may know, there are some (actually lots of) words that is very difficult to translate to another language.
In my experience, the most difficult English word for translating is “sinus”.
One day, maybe three years ago, my British friend asked me to go to a drugstore with him.
He had a problem with his sinuses and wanted to buy a medicine for that.
It was my first time to hear the word “sinus”.
He explained a lot about “sinus” , but I had no idea.
Finally we looked for a dictionary.
In my dictionary (my dictionary is named “Genius” which is the most famous dictionary in Japan.) there are some translating.
洞（とう ・ tou）
瘻（ろう ・ rou）
湾曲（わんきょく ・ wankyoku）
湾曲部（わんきょくぶ ・ wankyokubu）
… I still had no idea.
We gave up and went to the drugstore and showd the pharmacist the translation.
But! She had no idea either!!
The interesting point is that we don’t have the “idea” of sinus.
Of course we sometimes have a problem with our nose, throat and ears, but we don’t think the organ “sinus”.
Ask your Japanese friends if they know sinus and if you find a good Japanese translation, let me know please!