1. Linear Measure
Line Segment - A measurable part of a line that consists of two points, called the endpoints, and all the points between them. A segment with endpoints S and T can be written as ST or TS. The length or measure of the segment is written as ST or TS.

2. Linear Measure
Betweenness - A point is between two other points on the same line if and only if its coordinate is between their coordinates. (A-B-C if and only if a<b<c or a>b>c) Given three collinear points X, Y, and Z, if Y is between X and Z, then XY + YZ = XZ.

3. Linear Measure
Congruent () – Segments that have the same length. When superimposed, things that are congruent coincide exactly. In figures, items that are congruent are given the same markings.
Constructions – Drawings made with a straightedge and compass.

4. a. Find the length of .
Answer: in.
Example 2-2c

5. b. Find the length of .
Answer: in.
Example 2-2d

6. a. Find SE.
Answer: in.
Example 2-4f

7. b. Find ON.
Answer: 3.7 cm
Example 2-4g

8. c. Find a and AB if AB 4a + 10, BC 3a – 5, and AC 19.
Answer:
Example 2-4h