What is the difference between an antibiotic and an antibacterial?
An antibacterial is any compound that will kill or at least slow down the growth of strictly bacteria, a domain of prokaryotes.

An antibiotic is often used synonymously, but denotes a compound that kills or slows down the growth of any cellular pathogen, prokaryotic or eukaryotic. So, certain antibiotics can kill bacteria, fungi and parasites but antibiotics have no effect on viruses and prions.