The term 'WORK UNIT OF' can be completed with the three letter word 'ERG'. An ERG is a unit of work or energy, equal to the work done by a force of one dyne acting over a distance of one centimeter. It is also used in measuring the rate of energy transfer, such as power or heat flow. The ERG is most commonly used in the field of physics, but it is also used in other sciences such as chemistry and engineering.