Dr. Erica Brozovsky, Ph.D. of the University of Texas at Austin and host of the PBS series Otherwords looks at the letter “R” and explains while it is normally considered a consonant, it also qualifies as a vowel.
There’s a good argument that R is at least sometimes, a vowel. …R is an incredibly weird letter with so many different sounds and functions. It’s a wonder that we use one symbol to represent them all. And how people pronounce that one letter can speak volumes about their history and social background.
Brozovsky also notes that it is the pronunciation of this very letter that differentiates certain accents within the English language.
Up to now, I’ve only been talking about the standard American pronunciation of R, but you’re probably aware that not all English speakers say it the same way. In fact, the pronunciation of R is one of the most vivid differentiators between English dialects.