Definition of "sigma" [‖Sig•ma]

• The 18th letter of the Greek alphabet. See Table at alphabet. (noun)
• A sigma factor. (noun)
• A sigma baryon. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• ""Three sigma" is a manufacturing concept used to control processes, a concept that I am intimately familiar with."
• "The standard of comparison, 125 [sigma], is shorter than most of the reaction times recorded, but since the time measured was always that from the breaking to the making of the circuit passing through the chronoscope it cannot be urged that there were errors resulting from the difference of magnetization which was caused by variations in the reaction time."
• "I called sigma support line and they gave mixed opinions."