1
- the eighteenth letter of the Greek alphabet (Σ, σ), transliterated as 's'希腊字母表中第十八个字母（译写为s）。
1.1
- The form ζ is used instead of σ at the end of a word. The uncial form, resembling the letter c, is also sometimes used.在词尾使用ζ形式代替σ.有时也使用类似字母c的安色尔字体形式。
1.2
Sigma
followed by Latin genitive Astronomy the eighteenth star in a constellation【天文】σ星（星座中第十八颗星）：Sigma Octantis.
南极座σ星。
1.3
- Chemistry & Physics relating to or denoting an electron or orbital with zero angular momentum about an internuclear axis【化, 物理】σ键。
词源
Greek.