Concerning medicine, what are the differences between antibiotics and antibacterials?
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.
Antibiotics are a broader range of antimicrobial compounds which can act on fungi, bacteria, and other compounds. Although antibacterials come under antibiotics, antibacterials can kill only bacteria.
Penicillin was the first discovered by Alexander Fleming antibiotic and antibacterial.
There are certian classes of compounds which are bacteriostatic, which will not allow bacteria to grow (Ampcillin kills dividing cells) in number.
The word antibiotic refers to metabolic products (chemical compounds) of one microorganism that has detrimental or inhibitory effect to another microorganism. These are kind of chemotherapeutic agents used for treatment of infectious disease or disease caused by proliferation of malignant cells.Although some are prepared synthetically but most of them are prepared by microbial synthesis for commercial purpose. The treatment of one antibiotic differs from another by its mode of action. Antibiotics also can have broad spectrum and narrow spectrum of action and it is also possible that out one antibiotic is more active than other antibiotic against a particular pathogen and the effect is more impressive. Antibiotics can be antibacterial ( only and only against bacteria, either inhibition, destruction or suppression of bacteria. E.g. Bacitracin), same way some antibiotics are antifungal like Nystatin and some may show antitumor activity anthramycin. Antibiotics sometimes also have non-medical use like growth stimulants in poultry and live-stock feeds.
Whereas Antibacterial agents are those agents which "specifically" show their action against bacteria. (broader spectrum of action than antibiotic) They can act bacteriocidal (agents which kill or destroy bacteria) or bacteriostatic (agents which hinder the normal growth and reproduction of bacteria without killing them). Antibacterial agents can be metabolic compounds of microbes (antibiotics), they can be physical agents like radiations, heat (at particular temp that can kill only bacteria) or antibacterial agents can also be chemical by nature like alcohols,halogens (Iodine, chlorine, chlorine compounds).
So we can say that antibiotics can be antibacterial agents but all antibacterial agents need not be antibiotic.