The term 'work or energy unit' can be defined by two different units of measurement: the JOULE (5 letters) and the ERG (3 letters). The JOULE is a derived unit of energy in the International System of Units (SI), and it is equal to the work done by a force of one newton when its point of application moves one meter in the direction of the force. The ERG is a unit of energy and mechanical work in the centimeter-gram-second system of units (CGS). It is equal to the work done by a force of one dyne when its point of application moves one centimeter in the direction of the force.