1The eighteenth letter of the Greek alphabet (Σ, σ), transliterated as ‘s’.
The form ς is used instead of σ at the end of a word. The uncial form, resembling the letter c, is also sometimes used‘He coined this latter term and employed the Greek letter lower case sigma to denote its population parameter.’
- ‘Alpha, rho, tau, sigma, omega, Ash went over the letters he saw in his mind while Lari just stared, apparently in her own little world.’
- ‘Finally, even if epsilon is the correct reading, in the letter space to its right, where Meritt read part of an iota, are traces of what appears to be a sigma.’
- ‘You know you have seen them - those people who walk around wearing paraphernalia emblazoned with odd symbols like phi, sigma, and pi.’
- 1.1Astronomy followed by Latin genitive The eighteenth star in a constellation.‘Sigma Octantis’
- ‘Finally, the final green beam of light was shot straight up at the constellation Sigma.’
- 1.2Chemistry Physics Relating to or denoting an electron or orbital with zero angular momentum about an internuclear axis.‘the σ orbital is localized symmetrically’
- ‘These conical intersections are fundamentally different from the ‘H-vinyl’ structures found in simple alkenes because they involve the interaction of four sigma electrons, as opposed to two pi electrons and two sigma electrons.’
- ‘The sigma bond occupies the internuclear space, and the two pi bonds are at 90° angles to each other surrounding the carbon-carbon internuclear space.’
- ‘The triple bond is composed of one sigma bond from overlap of sp hybrid orbitals, and two pi bonds, from overlap of two sets of p orbitals.’
- ‘The sigma particles can be positive, negative, or neutral.’
1(also Σ)Mathematical sum.
2(also σ)Standard deviation.
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