A baker's dozen, also known as a 'piece to a dozen,' is a conversion representing 13 items instead of the standard 12. This extra item originated in medieval England to avoid penalties for shortchanging customers. The conversion involves the units of measurement, where one dozen equals 12 items, and a baker's dozen equals 13 items. This concept has practical applications in baking, where adding an extra item ensures that customers receive more than the expected quantity. In scientific contexts, the baker's dozen is used to illustrate the concept of a 'buffer' or 'safety margin,' where an extra item provides a safeguard against potential errors or uncertainties.