The "most probable number" (MPN) is a statistical method used to estimate the concentration of viable microorganisms in a sample. It is particularly useful in microbiology for assessing water quality or food safety. The MPN is determined by performing a series of dilutions and observing the growth of bacteria in specific media, allowing researchers to infer the number of organisms present. This technique is based on the principle of probability and is often used when direct counting methods, like colony-forming units (CFU), are impractical. The MPN provides a range of values, giving an estimate rather than an exact count, which is helpful in various scientific and industrial applications.