sig·​ma | \ ˈsig-mə \

Definition of sigma

1 : the 18th letter of the Greek alphabet — see Alphabet Table

Examples of sigma in a Sentence

Recent Examples on the Web

Typically, only five sigma is needed to call something a discovery. John Timmer, Ars Technica, "Visitor from another solar system accelerated away from the Sun," 28 June 2018 Physicists and astronomers, however, aren't usually convinced that two phenomena are connected until there's no more than a one in 3.5 million, or 5 sigma, probability of a coincidence. Daniel Clery, Science | AAAS, "Ghostly particle caught in polar ice ushers in new way to look at the universe," 12 July 2018 Physics requires a statistical significance of five sigma to declare discovery; MiniBooNE is tantalizingly close and will probably be there within the next two years. John Timmer, Ars Technica, "Weird neutrino excess won’t go away, hints at new physics," 8 June 2018 The MiniBooNE result had a standard deviation measured at 4.8 sigma, just shy of the 5.0 threshold physicists look for. NBC News, "A major physics experiment just detected a particle that shouldn't exist," 3 June 2018 Mattie was committed to serving her community and demonstrated this through her membership in Broward Alumnae Chapter, Delta sigma Theta Sorority, Inc. and Fort Lauderdale Chapter, The Links, Inc., "Deaths in South Florida: 4/27," 27 Apr. 2018 The difference between the two measurements has a significance of 2.4 sigma. John Timmer, Ars Technica, "A physical constant’s value shouldn’t depend on how you measure it," 13 Apr. 2018 The sigma of the Russia probes has been impossible for Trump to shake. Julie Pace And Vivian Salama, USA TODAY, "Trump to meet top Russian diplomat at the White House," 10 May 2017 The sigma of the Russia probes has been impossible for Trump to shake. Julie Pace And Vivian Salama, USA TODAY, "Trump to meet top Russian diplomat at the White House," 10 May 2017

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'sigma.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of sigma

1584, in the meaning defined at sense 1

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The first known use of sigma was in 1584

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English Language Learners Definition of sigma

: the 18th letter of the Greek alphabet

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irregularly rounded

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