[ 'sɪgmə ]
■ noun
1》 the eighteenth letter of the Greek alphabet ( Σ , σ , or at the end of a word ς ), transliterated as ‘s’.
2》 [as modifier ] Chemistry & Physics (of an electron or orbital) with zero angular momentum about an internuclear axis.
■ symbol
1》 ( Σ ) mathematical sum.
2》 ( σ ) standard deviation.
Origin
from Gk.