Diphthong. It's a funny word. Try not to divide it into two. As naughty as the term may sound, diphthongs are actually complex and compound vowels. You'll see them in Korean text on a daily basis.
Let's learn about diphthongs with Professor Oh in Lesson 4:
There are 11 diphthongs in the Korean language. A diphthong starts with one vowel sound and ends with another.
To download the following worksheet, right click on your mouse. Then press "Save Image as..." and save to your intended location. Have fun practicing your Korean skills!