R-controlled vowels are also known as bossy r vowels.  occur when the letter "r" changes the sound of a preceding vowel in a word. In these instances, the "r" controls or influences the pronunciation of the vowel. Examples of Rcontrolled vowels are:​ "ar" as in "car" or "far", ​"er" as in "her" or "fern", "ir" as in "bird" or "stir","or" as in "fork" or "corn","ur" as in "turn" or "burn"