internal angle

4.2

The angle inside a polygon where two sides meet

noun

Specialized

: ángulo interno

The internal angle increases as the number of sides in a regular polygon increases.

Examples

The internal angle is acute.
To find the sum of the internal angles in a polygon, use the formula (n-2) × 180.
Each internal angle of a regular pentagon measures 108 degrees.
The internal angle of a triangle is always less than 180 degrees.
In a triangle, the sum of the three internal angles is always 180 degrees.
To calculate the area of a polygon, you need to know the measures of the internal angles formed by its sides.
He drew a diagram to show how the internal angles of a square are all right angles.

Synonyms

interior angle

vsinternal angle

Specialized

1 3.9

The space inside a shape with straight sides where two sides meet

means the same but uses a different common adjective in the name

How Internal

internal angle

Specialized

4.2

external angle

Specialized

6.3

Surface Forms

internal angle singular

internal angles plural

Morphology

internal + angle

The meaning is directly derivable from combining 'internal' (inside/within) and 'angle' (the measure between two lines): it simply denotes an angle on the inside of a polygon where two sides meet. This adjectival+noun compositional pattern is standard in geometry and cross-linguistically common, so a B1 learner who knows both constituents would readily understand it.

Etymology

Internal angle paints a simple picture: internal means 'inside' and angle is the space between two lines. So an internal angle is the corner formed where two sides meet inside a polygon, which is why the term refers to the angle 'inside' the shape.