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Webster 1913 Edition
Sigmoidal
{
Sig′moid
,Sig-moid′al
, }Adj.
[Gr. [GREEK][GREEK][GREEK]; [GREEK][GREEK][GREEK] sigma +
εἶδοσ
form, likeness: cf. F. sigmoïde
.] Curved in two directions, like the letter S, or the Greek ς.
Webster 1828 Edition
Sigmoidal
SIGMOID'AL
,Adj.