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icos-

Also eicos‑

Twenty.

Greek eikosi, twenty.

An icosahedron is a solid figure with twenty plane faces, especially equilateral triangular ones; an icosidodecahedron (Greek dodeka, twelve) is a solid with 32 faces, 20 equilateral triangles and 12 regular pentagons. Eicosapentaenoic acid, so named because it contains 20 carbon atoms, is a fatty acid found especially in fish oils, a metabolic precursor of prostaglandins; the eicosanoids are a group of hormones and other biologically active substances similarly containing 20 carbon atoms, including leucotrienes, prostaglandins, and thromboxanes.

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