hey masanori,
the "story" refers to the single post you make in the story form (the box on top where you enter your status text, share your link etc.) while the "stream" is the global representation, the place where all the different shared items come together. hope that makes sense and helps with your translation

Yep, Alex is on the right spot here. In a much simpler layman term, "you write a story on your stream". You don't "write a stream on a stream"

Hi guys,

Thank you for the explanation, I understood.
I appreciate it if you could let me know the differences of following words...
Update<vs>Story
Stream Item<vs>Feed

Mark,

Thank you!
I understand it.
I'll make some efforts to translate....

No problem Masanori