Jisho

When asking about a word, I would recommend providing as much context as you can, even if you think people should be able to answer without it. It just saves a lot of back and forth. Where did you see it? What was the full sentence? What kind of person said it? And so on.

@Priyabrat Why did you copy what I said in the 見られづ thread here... This isn't about context, it's about disambiguating two common words. Presumably they didn't see the words in some context, they just encountered them in the dictionary.

And it's also just weird to copy what someone else wrote exactly and act like you said it, but whatever.

It's completely diffferent.
別巻: different volumes IN A SERIES. (i think this is the meaning you would imagine when reading the english translation)
別冊: this referring to a publication added to the main volume or articles to summerize all the footnote/refference/comments et cetera. (i dont work in publishing and dont often read these things so I'm not sure if this makes sense sr xd)
bessatsu can also refer to a limited edition

@Lyza thank you, it's kind of what I imagined. I'm trying to write something about a welcome to an specific volume of a series and I crossed with both words and didn't know which one to pick because I didn't get the difference between. Thank you!