What two vowels when placed together will make one sound?

This is a bit of a trick question! There are many ways to answer, depending on what you mean by "one sound." Here are a few possibilities:

* Diphthongs: These are vowel combinations that create a single, gliding sound. Some common examples include:

* "ou" as in "out"

* "oi" as in "oil"

* "ai" as in "rain"

* "ey" as in "they"

* "ea" as in "meat"

* Double vowels: Sometimes two vowels are written together but only one is pronounced. This happens when the first vowel is silent:

* "ea" as in "bread" (the "e" is silent)

* "ai" as in "said" (the "a" is silent)

* Single vowel sounds: Some vowel combinations are pronounced as a single vowel sound, but they don't necessarily form a diphthong:

* "ee" as in "see" (sounds like the single vowel sound /i/)

* "oo" as in "moon" (sounds like the single vowel sound /u/)

So, the answer really depends on what you're looking for! Do you want a combination that makes a gliding sound, or just a single vowel sound?