Let’s talk about what a **vector** is. Vectors are often important in science and engineering for describing real-world problems in the language of mathematics. Say you’ve got a nice Smart Car, and you want to tell someone how fast you’re driving it. **Speed is a scalar quantity**, consisting of a number and some units. You can give your speed as 45 mph. (Or even better 20.1 m/s which we like because it’s in SI units!)

But what if you wanted to give your velocity? **Velocity is different than speed, because it’s a vector quantity.** This means the **direction** is also important. For example, check out the lower Smart Car, which is going 45 mph at a 30-degree angle to the x-axis. This is a velocity, because we’ve given the speed (magnitude) and the direction.