Geometry Vocabulary

Front

What is a coplanar point?

Back

Points that lie on the same plane.

Front

What is a line segment?

Back

A geometric object that is finite and has 2 endpoints.

Front

What is the notation for a line segment?

Back

A line segment is denoted by the endpoints, e.g., AB.

Front

What are undefined terms in geometry?

Back

Basic concepts that do not have formal definitions, such as point, line, and plane.

Front

What are defined terms in geometry?

Back

Terms that have formal definitions, such as angle, triangle, and circle.

Front

What is an acute angle?

Back

An angle that is less than 90 degrees.

Front

What is a right angle?

Back

An angle that is exactly 90 degrees.

Front

What is an obtuse angle?

Back

An angle that is greater than 90 degrees but less than 180 degrees.

Front

What is a straight angle?

Back

An angle that is exactly 180 degrees.

Front

What is a ray in geometry?

Back

A part of a line that starts at a point and extends infinitely in one direction.