1 a : curved like the letter C
b : curved in two directions like the letter S
2 : of, relating to, or being the sigmoid colon
Did You Know?
The shape sense of "sigmoid" is most often used in scientific contexts to describe an s-shaped curve on a graph. Usually, though, "sigmoid" is used in contexts relating to the sigmoid colon-the contracted and crooked part of the colon immediately above the rectum. "Sigmoid" comes from "sigma," the name of the 18th letter of the Greek alphabet. At one time sigma had a common form that was shaped like the Roman letter C (hence sense 1a), but sigma is equivalent to the English letter S (hence sense 1b).
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Glancing out the airplane's window, I could see the sigmoid curvature of the river below us.
"In my opinion, Missouri's deer herd is following the classic sigmoid population curve. The sigmoid curve is 'S' shaped with slow growth on the left side, very rapid growth in the middle, followed by population maintenance as the population reaches carrying capacity for the habitat." -- From an article by Spencer E. Turner in Missouri's Columbia Daily Tribune, January 6, 2008 Sunday
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