Sigma Xi (Xi is pronounced with a "Z" sound-"Zi"-as in "xylophone") was founded in 1886 to honor excellence in scientific investigation and encourage a sense of companionship and cooperation among researchers in all fields of science and engineering. The Greek letters "sigma" and "xi" form the acronym of the Society's motto, "Spoudon Xynones," which translates as "Companions in Zealous Research."