LESSON 2 Lines

Have you ever thought about lines? You can draw a line or you can make a line with a string. Some lines are straight, like a jet trail in the sky, the edge of a piece of paper, or a piece of uncooked spaghetti.

Some lines are curvy, like a winding road or the letter “S.”

Some lines are jagged like a mountain range or a zigzag decoration on a shirt.

In geometry, if we talk about a line, we mean a straight line. For the rest of this unit, we will always mean straight line when we say line.

A line in geometry goes on forever in both directions. It has no beginning or end. We cannot draw a picture of a whole line so we put arrows at the ends to show that the line keeps going on infinitely (forever).

Lines are often named by two points on the line. This is line AC.

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We write . We can also call it or .

A line segment is a part of a line with two end points. Line segment AB is the part of the line between the end points marked A and B. We write to show that we mean only this segment and not any other part of the line.

1. Name two other line segments that are part of .