One of the seven basic tools for problem solving. A schematic sketch, usually resembling a fishbone, which illustrates the main causes and subcauses leading to an effect (symptom). Also known as Fishbone Diagram., Ishikawa Diagram and Root Cause Analysis. Spine represents the “effect” and the major legs of the structure are the “cause categories.” The substructure represents the list of potential causes which can induce the “effect.” The 6M’s (man, machine, material, method, measurements and mother nature, are sometimes used as cause categories.