Lines, Segments, Rays, and Angles

a line goes on and on in both directions

we show this by putting "arrowheads" on each end

a segment is part of a line

we show a line segment by putting dots on each end

the dots show that the line has a starting point and a stopping point

it begins at one point and continues on in one direction without end

we show this by adding an arrowhead on one end and a dot on the other

A point in geometry is a location. It has no size (no width, no length, and no depth)

A point is shown by a dot

Lines and segments that go in the same direction and stay the same distance apart are called parallel.

When lines or segments cross, we call them intersecting lines.

Intersecting lines or segments that form "square corners" are perpendicular.

Angles are formed where lines or segments intersect.

Angles are also formed where at least two rays begin.

An angle has a vertex and two sides.

An angle is named by how open it is.

The angle like the corner of a square is called a right angle.

To show that an angle is a right angle, we can draw a small square in the corner.

Angles that are smaller than right angles are called acute angles.

Angles that are larger than right angles are called obtuse angles.