interior angle

noun

, Geometry.

1. an angle formed between parallel lines by a third line that intersects them.
2. an angle formed within a polygon by two adjacent sides.

interior angle

noun

1. an angle of a polygon contained between two adjacent sides
2. any of the four angles made by a transversal that lie inside the region between the two intersected lines

interior angle

/ ĭn-tîr′ē-ər /

1. Any of the four angles formed inside two straight lines when these lines are intersected by a third straight line.
2. An angle formed by two adjacent sides of a polygon and included within the polygon.
3. Compare exterior angle

Word History and Origins

Origin of interior angle¹

First recorded in 1750–60

Example Sentences

We learn that the interior angles of triangles add up to 180°.

From Scientific American

I got the first cut, but again, when I started cutting the interior angle, the bar worked its way out of the jig, and the tool dug in and broke.

From Literature

I think this is fascinating because it means that in other geometries, there are triangles that have different sums of interior angles!

From Scientific American

Each interior angle of a regular heptagon is a bit over 128 degrees, so when we put three of them together at a vertex, we get more than 360 degrees.

From Scientific American

Squinch, skwinch, n. a small stone arch, or series of arches, across an interior angle of a square tower to support the sides of an octagonal spire.

From Project Gutenberg