A "ratio" is a relationship between two numbers, like:

• 4:1 ("four to one")
• 3:2 ("three to two")
• 10:1 ("ten to one")

Devices that have screens, like TVs, phones, tablet computers, and so on have an "aspect ratio", which is the relationship between the width and height of the screen. Some common aspec ratios are 16:9, 4:3, and 3:2.

When you say the aspect ratio of a device out loud, you might say it as "___ by ___" instead of "___ to ___":

It's a sixteen by nine device.