In the system of time study of manufacturing labor devised by Frank Bunker Gilbreth and Lillian Moller Gilbreth, the smallest observed and recorded unit of task. It was first described in print in 1924¹, but was in use by them before that time and continues to be used. Examples of therbligs include “hold”, “position”, and “disassemble”; there are about 18. The word is “gilbreth” spelled backwards, taking “th” as the digraph it is.

1. Frank B. Gilbreth and L. M. Gilbreth.
Classifying the elements of Work. Methods of Analyzing Work into Seventeen Subdivisions.
Management and Administration, volume 7, no 8 (August 1924). Pages 151 – 154. Quotation below is from page 152.
Frank B. Gilbreth and L. M. Gilbreth.
Applications of Motion Study. Its Use in Developing Best Methods of Work.
Management and Administration, volume 7, no 9 (September 1924). Pages 295 – 297.

...subdivisions, or events. or therbligs² of a cycle of motions which consists of...

2. This word was coined for the purpose of having a short word which will save the motions necessary to write such long descriptions as “The 17 categories into which the motion-study elementary subdivisions of a cycle of motions fall.”

This periodical went through a confusing number of name changes. Before July 1923 it was Administration. In January 1926 it changed its name to Management and Administration in Manufacturing Industries, and in March 1929 was absorbed by Factory and Industrial Management


An enthusiastic, good account of the topic, including descriptions of each of the 18 therbligs, can be found online at


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