Diphthongs, Blends & Digraphs I had no idea what these were when I first began teaching phonics. Not that I needed to know what these terms meant in order to teach phonics well, but it did help when it came to sorting out the different combinations in my head as I was teaching them. Here are the basic differences between Diphthongs, Blends, and Digraphs: Blends - Consonant Blends include letter combinations like st, pr, and nk. You can hear the individual sounds even as you are blending them. Digraphs - Digraphs include letter combinations like oo and ew. They only make one single sound when blended together. Diphthongs - Diphthongs include letter combinations like ai and oa. They make one sound that morphs into a second sound when blended together. (For example, "ai" sounds like "aaaeeee" if you say it really slowly, like a long a morphing into a long e sound  .)