Learn to describe figures by using the terms of geometry.

Vocabulary point line plane line segment ray

The building blocks of geometry are points, lines, and planes.

Additional Example 1: Identifying Points, Lines, and Planes Use the diagram to name the geometric figure. A. three points M, N, and P Five points are labeled: points M, N, P, Q, and R. B. two lines PR and NR You can also write RP and RN.

Additional Example 1: Identifying Points, Lines, and Planes Use the diagram to name the geometric figure. C. a point shared by two lines point R Point R is a point on PR and NR. D. a plane plane QRM Use any three points in the plane that are not on the same line. Write the three points in any order.

Use the diagram to name the geometric figure. Check It Out: Example 1 Use the diagram to name the geometric figure. A. three points S, T, and U Five points are labeled: points S, T, U, V, and W. V S U W T B. two lines UW and SW You can also write WU and WS.

Use the diagram to name the geometric figure. Check It Out: Example 1 Use the diagram to name the geometric figure. C. a point shared by two lines point W Point W is a point on WS and WU. V S U W T D. a plane plane VUT Use any three points in the plane that are not on the same line. Write the three points in any order.

Additional Example 2: Identifying Line Segments and Rays Use the diagram to give a possible name to the figure. A. three different line segments C A B AB, BC, and AC You can also write BA, CB, and CA. B. three ways to name the line AB, BC, and AC You can also write BA, CB, and CA.

Additional Example 2: Identifying Line Segments and Rays Use the diagram to give a possible name to the figure. C. six rays C A B AB, AC, BC, CB, CA, and BA D. another name for ray AB AC A is still the endpoint. C is another point on the ray.

A. three different line segments Check It Out: Example 2 Use the diagram to give a possible name to the figure. A. three different line segments F D E DE, EF, and DF You can also write ED, FE, and FD. B. three ways to name the line DE, EF, and DF You can also write ED, FE, and FD.

D. another name for ray DE Check It Out: Example 2 Use the diagram to give a possible name to the figure. C. six rays F D E DE, EF, DF, FE, FD, and ED D. another name for ray DE DF D is still the endpoint. F is another point on the ray.

Lesson Quiz Use the diagram to name each geometric figure. 1. three points 2. two lines 3. a point shared by a line and a ray 4. a plane Possible answer: A, B, C Possible answer: AD, CE Possible answer: F Possible answer: plane AEC