We are going to take a look at some **straight lines** in today’s post. The first thing that’s on the agenda is to define what exactly straight lines are in order to differentiate them from curved lines. Then, we’ll have a look at the concepts of rays, line segments and open rays.

##### What is a line?

Every **line** is made up of points, which is the smallest graphic unit.

A series of points that are lined up one after another make a continuous streak, which we will call a “line”.

When the points always go in the same direction, they form **a straight line**. Imagine if we could see each and every one of those points that form a line, it would probably look something like this.

When the points, while still maintaining an order, constantly change direction, they form **a curved line**. If we could see each and every one of the points of a curved line, it might look something like this.

##### What is a ray?

A **ray** is a straight, infinite line: it never ends. It’s impossible to visually represent these lines so we draw rays without a point on its ends, understanding that this means that the line doesn’t stop there but rather, it keeps going on until infinity.

To name a ray, we use lowercase letters, for example:

However, we can also cap off these rays, and by doing this, the ray would become a line segment. Each one of this segment’s ends represents the last point of the ray. These points, or ends, are written in uppercase and are named according its two ends:

**Segment AB**

If we limit this ray only on one of its sides, the result is an open ray. The open ray starts with a point, which we will call the origin, and from there, it goes on until infinity. We also give the origin a name with an uppercase letter:

And that’s all for today. What did you think about this post? **Did it help you understand what straight lines are**?

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### Learn More:

- Learn about Open and Closed Curves
- Straight and Curved Lines – Geometry
- Geometric Figures and Straight Lines
- How to Identify Open and Closed Polygons
- Locating Numbers on the Number Line

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