R is an unusual letter. Normally it is a consonant. Sometimes it acts as a vowel. But something even more amazing is that it sometimes has the power to change the sound of a vowel in front of it.
R AS A CONSONANT
In words such as “run”, “carrot” or “free” R is a consonant.
R AS A VOWEL
In some words, the R takes the place of the vowel. That is, the vowel before the R becomes silent, because the R dominates — it takes away, or covers up the vowel sound.
Here are some examples: earth, chirp, curve, govern, her, iceberg, term, third, shirt, surf, verse, work, worst. This is a short list of examples — there are quite a few words like this.
The loss of the vowel sound also happens with -er and -or at the ends of words, as in “other” and “actor”.
R can sometimes change the sound of a vowel, instead of covering it up.
A changing to O
This happens when an “a” is trapped between a “w” or “u” and an “r”. For example, the word “war” sounds like the word “wore” — they are homonyms. “Warn” and “worn” are also homonyms. However, “warm” and “worm” do not sound the same, because “worm” has R as a vowel.
Other words in which the “a” sounds like “o” are: award, dwarf, quart, quarter, quartz, thwart, ward, warm, warp, wart, wharf.
Why does this happen? The “w” or “u” sound and the American “r” sound are all made with rounded lips. So an “a” trapped between these sounds also gets pronounced with rounded lips — native speakers don’t unround their lips just for the “a” in between. An “a” with rounded lips ends up sounding like “o”.
E changing to A
This happens in a few words that have an “e” before an “r”. To make an “r” sound, the tongue needs to be very tense, and this tension affects the “e”, making it sound more like an “a”.
Here are some common words:
where (this is a homonym with “ware”)
merry (this is a homonym with “marry”)
very (this is a homonym with “vary”)
So, two good things to keep in mind when dealing with R are: First, don’t be surprised if you find some words that are pronounced with an unexpected vowel sound when R follows. Second, listen closely when R is involved, so that you can hear how to pronounce those words correctly.