What does equiangular mean?
Equiangular is an adjective from geometry describing a figure whose angles are all equal in measure. An equiangular polygon has interior angles that are identical — a rectangle, for instance, is equiangular because each of its corners is a right angle, even though its sides need not be equal in length. The word is most often met in discussions of polygons and triangles: in a triangle, being equiangular automatically makes it equilateral as well, though for figures with more sides this equivalence fails. The term also appears in the phrase 'equiangular spiral', another name for the logarithmic spiral found throughout nature, from nautilus shells to spiral galaxies, which cuts every radius from its center at a constant angle. Precise and technical rather than conversational, equiangular is valuable chiefly to students of mathematics and anyone describing shapes with exactness.
Having all angles equal; especially said of a polygon whose interior angles are all of the same measure.
"A regular hexagon is both equiangular and equilateral."
In mathematics, 'regular' means both equiangular and equilateral; the two terms are distinct for most polygons.
(Of a spiral) Cutting every radius drawn from its center at a constant angle; logarithmic.
"The chambered nautilus builds its shell along an equiangular spiral."
In triangles, equal angles guarantee equal sides — but stretch that polygon to four sides and the guarantee vanishes: a rectangle is equiangular without being equilateral.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of equiangular
Equiangular comes from the Latin aequus ('equal') combined with angulus ('angle'), a compound patterned after earlier geometric terms such as equilateral. It entered English in the early modern period as mathematicians adopted Latin-derived terminology for describing figures precisely. It shares the same roots with words like equilateral, equidistant, and angular.
How equiangular is actually used
Equiangular is a technical term belonging chiefly to geometry and mathematics; it appears rarely outside academic, educational, or scientific writing. It carries no emotional connotation and is register-neutral but formal-leaning by nature of its subject matter.
Easily confused with equiangular
Equilateral means having all sides of equal length, while equiangular means having all angles of equal measure — the two coincide in triangles but not in general polygons.