The meaning of these terms sterile and sterilization is absolute; there is no such thing as a “practically sterile” or “nearly sterile” object. A thing is either sterile, or it is not sterile.
Disinfection means the destruction of pathogenic microorganisms. The term disinfectant is applied to an agent, usually a chemical, which is used to destroy disease-producing organisms.
Of course, it may kill harmless bacteria, too, but it happens that disease germs are, in general, more easily destroyed than the harmless saprophytic types, so that disinfection may be accomplished in many instances with agents that do not truly sterilize.
Thus, the feces of a typhoid patient may be successfully disinfected with a chemical which kills the typhoid germs, even though it does not destroy all the bacteria present.
Any agent that kills micro-organisms may be called a germicide.
This refers to a condition which bacteria are prevented from multiplying, though not killed. Low temperatures, weak concentrations of germicides, and certain dyes for example, may keep bacteria in a state of suspended animation, and so are said to have a bacteriostatic effect.
This term and the more widely employed derivative antiseptic cannot be defined very satisfactorily. Literally, an antiseptic is a substance that opposes sepsis, a world derived from the Greek meaning rotting, putrefaction, and decay.
Since it is the growth of micro-organisms that causes sepsis, an antiseptic must have the property of preventing the multiplication of microbes, or in other, words, it must have a bacteriostatic effect. It may be a much weaker agent than a disinfectant, for the latter actually destroys germs
Unfortunately most laymen and many doctors do not use antiseptic in this strict and literal sense, but give it the same meaning as disinfectant. In consequence, an “antiseptic” in current usuage may refer to a truly germicidal agent in one case, or to a substance that has merely a bacteriostatic action in another case.
It is best for professional people to employ the term only in its literal sense to mean an agent that inhibits the growth of microbes, without destroying them.