Printer's Unit is a unit of measurement used in the printing industry. It is composed of three parts: REAM (4 letters), PICA (4 letters), and Emquad (6 letters). A REAM is a unit of paper that is equal to 500 sheets. A PICA is a unit of measurement that is equal to 1/6 of an inch. An Emquad is a unit of measurement that is equal to 1/18 of an inch. Together, these three units make up the Printer's Unit, which is used to measure the size of typefaces and other elements in the printing process.