Someone say yes. someone say no. Could anyone explain easily in scientific way?
Maybe this quote be perfect for beginning discussion.
this has somewhat fazed me as well... the original bitcoin didn't have segwit and didn't have larger blocks, so, the bitcoin running now, which has segwit, and the forked one - bitcoin cash, whose blocksize was increased, are both modifications of the original.
so that means the original bitcoin is gone (?) 
Maybe this quote be perfect for beginning discussion.
Yes because it is (BTC Cash)a divergence from the current bitcoin so would mean it is an alternative version of bitcoin so altcoin it is, regardless if more people support it and it becomes the leader it is still an altcoin, in my eyes anyway.
this has somewhat fazed me as well... the original bitcoin didn't have segwit and didn't have larger blocks, so, the bitcoin running now, which has segwit, and the forked one - bitcoin cash, whose blocksize was increased, are both modifications of the original.
so that means the original bitcoin is gone (?) You will never get a scientific answer because there isn't one
Most of the time, the word "altcoin" is used by juveniles as a pejorative term to denigrate a coin's status and credibility. That is all.