The 18th letter of the Greek alphabet (Σ, σ); used in mathematics to denote summation.
From Greek 'sigma,' ultimately from Phoenician 'samekh.' The letter shape evolved from the Phoenician character resembling a pillar or support. In mathematics, chosen for summation because it begins the Greek word 'sum.'
Sigma's distinctive final form (ς) only appears at the end of Greek words, making it unique among Greek letters for having a positional variant. In internet culture, 'sigma male' has emerged as slang for an independent, self-reliant person, showing how ancient symbols continuously acquire new meanings.
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