View source for Σ

{{also|σ|ς|∑|ⵉ|Ʃ|σ.|σ'}}
{{character info}}
==Translingual==

===Symbol===
{{head|mul|symbol}}

# {{lb|mul|mathematics}} '''Σ'''. [[sum|Sum]] over a [[set]] of like [[terms]]:
#: <math>\sum_{n=1}^3 n^2 = 1^2 + 2^2 + 3^2 = 14</math>
# {{lb|mul|topology}} [[suspension]] or [[reduced suspension]]
# {{lb|mul|mathematics}} A class (in the [[w:arithmetical hierarchy|arithmetical hierarchy]]) of [[formula]]e whose outermost unbounded [[quantifier]]s are [[existential quantifier]]s

====Usage notes====
{{sense|mathematics}} Though there exists a distinct symbol ([[∑]]) for the purpose of the mathematical summation, the upper case sigma here is often used for convenience.

====Coordinate terms====
* {{sense|classification of formulae}} {{l|mul|Π}}, {{l|mul|Δ}}

===See also===
* {{pedia}}

==Ancient Greek==

===Alternative forms===
* {{alt|grc|Ϲ}}

===Etymology===
From {{bor|grc|phn|𐤔|t=šīn}}.

===Letter===
{{head|grc|letter|uppercase||nonfinal lowercase|σ|final lowercase|ς}}

# The letter [[sigma]] ({{l|grc|σίγμα|tr=-}}), the 18th letter of the ancient [[Greek alphabet]].

====Derived terms====
* {{qualifier|[[Cyrillic]]}} {{l|mul|С|sc=Cyrl}}
* {{qualifier|[[Coptic]]}} {{l|cop|Ⲥ|tr=-}}

====See also====
{{Grek-script}}

==Greek==

===Letter===
{{head|el|letter|uppercase||lowercase|σ}}

# The [[upper case]] letter [[sigma]] ([[σίγμα]]), the 18th letter of the modern [[w:Greek alphabet|Greek alphabet]].

===Numeral===
{{head|el|numeral}}

# The number 200 in [[w:Greek numerals|Greek numerals]].

''',Σ'''
# The number 200,000 in Greek numerals.

===See also===
: ''see:'' [[Appendix:Greek alphabet]]