An antimicrobial or antibiotic is an agent that kills microorganisms or inhibits their growth. Antimicrobial medicines can be grouped according to the microorganisms they act primarily against. For example, antibacterials are used against bacteria and antifungals are used against fungi. They can also be classed according to their function. Antimicrobials that kill microbes are called microbicidal; those that merely inhibit their growth are called microbiostatic. Antiseptics help reduce infection during surgery. Disinfectants such as bleach are nonselective antimicrobials. They kill a wide range of microbes and are valuable for cleaning inanimate surfaces to prevent the spread of illness, but they are generally not medicinal.