Some words are homophones in American English but not in British English. Why? Because Americans do something called "alveolar flapping."
A couple of months ago, I answered a listener’s question about how to remember the meanings of the adjectives hearty, spelled H-E-A-R-T-Y and hardy, spelled H-A-R-D-Y. I said that the words were confusing because their meanings overlapped somewhat, and this is true, but there’s another reason for the difficulty in keeping these words straight: They’re homophones!
Some Words Are Homophones in American English but Not British English
At least, they’re homophones in American English. In British English, though, they’re not; they’re pronounced [hɑrti] and [hɑrdi]. Actually, they’re not pronounced that way, either; they’re pronounced in any one of the many accents of British English, which I won’t embarrass myself by trying to imitate. The point is, the T in [hɑrti] sounds like a T, and the D in [hɑrdi] sounds like a D.
In fact, there are many pairs of words that are homophones in American English because we pronounce a T in one of them like a D. For example, there’s ladder the device that you climb, and latter as opposed to former. There’s riding as in horseback riding, and writing as in Quick and Dirty Tips for Better Writing. (If you’re listening to this podcast for tips on equitation, sorry; this isn’t the podcast for you.) There’s Bode as in Bode Miller, and Boaty as in Boaty McBoatface. This phenomenon is also what lets us make a rhyme when we say Work smarter, not harder.
How Alveolar Flapping Makes Some Words Homophones
So why do we do this in American English, and how long have we been doing it? First, we need a word for what to call this pronunciation quirk. The linguistic term for it is alveolar tapping or alveolar flapping. The word alveolar refers to the alveolar ridges in your mouth. What are those? I’m glad you asked. The alveolar ridges are the bony, gum-covered ridges behind your front teeth. You have an upper one and a lower one, but when phoneticians talk about an alveolar ridge, they’re almost always talking about the upper one, because that’s where you put the tip of your tongue to make so-called alveolar consonants. T and D are alveolar consonants; so are N and a few others. Go ahead and make a T, D, or N sound right now, and you’ll feel your tongue-tip on your alveolar ridge.
An alveolar tap or flap is made by putting that tongue tip on the alveolar ridge so quickly that it doesn’t really stop the airflow the way a true T does. Some phoneticians have argued that there’s a difference between tapping and flapping, which I won’t try to describe here. These days, the opinion seems to be that whatever difference there is isn’t important, so tap and flap are often used as synonyms. I’ll use the word flap, since it seems to be somewhat more popular.