Therbligs

Therbligs are a set of eighteen basic elemental motions, such as reach, grasp, move, position and release, that the engineers Frank and Lillian Gilbreth identified in the 1910s as the fundamental building blocks any manual task can be broken down into for analysis. The name is the Gilbreths' own surname spelled almost backward, a coinage frequently attributed to their work together at the Gilbreth Motion Study company. By reducing any manual job to a sequence of therbligs, each labeled with its own symbol and typical duration, an analyst could identify which elemental motions were wasteful or unnecessary and redesign the task around only the efficient ones, extending the Gilbreths' broader motion-study work into a standardized notation still referenced in industrial engineering education.