entasis

American  

[en-tuh-sis] / ˈɛn tə sɪs /

noun

Architecture.

1. a slight convexity given to a column or tower, as to correct an optical illusion.

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entasis British  

/ ˈɛntəsɪs /

noun

1. a slightly convex curve given to the shaft of a column, pier, or similar structure, to correct the illusion of concavity produced by a straight shaft

2. Also called: entasia.  physiol an involuntary or spasmodic muscular contraction

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Etymology

Origin of entasis

1745–55; < Greek, equivalent to enta- (variant stem of enteínein to stretch tight, equivalent to en- en- ² + teínein to stretch) + -sis -sis

Example Sentences

The ancient Greeks made their columns bulge out slightly about a third of the way up to correct for the optical illusion of concavity — a technique known as entasis.

From Washington Post

A column of the Parthenon, with its inclination, its tapering, its entasis, and its fluting, could not have been constructed without the most conscientious skill.

From A History of Greek Art by Tarbell, Frank Bigelow

Sometimes they would give it, with exaggerated refinement, the entasis of the Greek column.

From The Atlantic Monthly, Volume 05, No. 27, January, 1860 by Various

The columns diminished at the top to about one-fifth of the lower diameter, and would seem to have had an entasis, as the lower portion up to one-third of the height is nearly vertical.

From Encyclopaedia Britannica, 11th Edition, Volume 2, Slice 4 "Aram, Eugene" to "Arcueil" by Various

This outward curvature of the profile is termed an entasis and in the Parthenon column, which is thirty-four feet in height, amounted to about three-fourths of an inch.

From Visual Illusions Their Causes, Characteristics and Applications by Luckiesh, Matthew