**Senses**

- [
*Geom*] A figure bounded by three lines, and containing three angles. - [
*Mus*] An instrument of percussion, usually made of a rod of steel, bent into the form of a triangle, open at one angle, and sounded by being struck with a small metallic rod. - A draughtsman's square in the form of a right-angled triangle.
- [
*Mus*] A kind of frame formed of three poles stuck in the ground and united at the top, to which soldiers were bound when undergoing corporal punishment, -- now disused. - [
*Astron*]- A small constellation situated between Aries and Andromeda.
- A small constellation near the South Pole, containing three bright stars.

- A small constellation situated between Aries and Andromeda.

** Note: **☞ A triangle is either *plane*
*spherical*
*or curvilinear*, according as its sides are straight lines, or arcs of great circles of a sphere, or any curved lines whatever. A plane triangle is designated as *scalene*
*isosceles*
*or equilateral*, according as it has no two sides equal, two sides equal, or all sides equal; and also as *right-angled*, or *oblique-angled*, according as it has one right angle, or none; and oblique-angled triangle is either *acute-angled*, or *obtuse-angled*, according as all the angles are acute, or one of them obtuse. The terms *scalene*
*isosceles*
*equilateral*
*right-angled*
*acute-angled*, and *obtuse-angled*, are applied to spherical triangles in the same sense as to plane triangles.

** Etymology: **L. *triangulum*, fr. *triangulus* triangular; *tri-*see Tri-) + *angulus* angle: cf. F. *triangle*. See Angle a corner