A suit jacket can be worn as a sport coat, but it is neither a blazer nor sport coat.
Wait what?
That was my reaction.
What is a blazer?
A blazer ONLY comes in navy and black featuring naval metal buttons. See Ralph Lauren example:
Many in the industry still consider any jacket with buttons and pointed collar a blazer, but that's not the case.
Any jacket that does not have matching pants is consider a sport coat.
A matching pair of pants with a jacket is called a suit.
Are you less confused now?