According to the EPA (Environmental Protection Agency), the following are standard definitions of clean, sanitize, and disinfect:
Clean – The process that physically removes debris from the surface or area by scrubbing, washing, and rinsing. It may be accomplished with soap or detergent and water.
Sanitize – A product that kills 99.9% of germs identified on its label. Sanitizers are used to reduce, but not necessarily eliminate microorganisms from the inanimate environment levels considered safe as determined by public health codes or regulations.
Disinfect – A product that kills nearly 100% of germs identified on its label. Disinfectants are used on hard inanimate surfaces and objects to destroy or irreversibly inactivate infectious fungi and bacteria, but not necessarily their spores. There are two major types of disinfectants: hospital and general use. Hospital disinfectants are the most critical to infection control while general disinfectants are typically used in households, swimming pools, and water purifiers.
The EPA lists more specific and technical details regarding the guidelines for sanitizers and disinfectants, but they go into far more detail than users generally need.