Want to know what a 55-year-old American will sound like in the year 2050? Listen to a 20-year-old American today. They're the same people, after all.

They won't sound exactly the same, of course. The way a given person speaks changes at least a little over the course of his or her life — especially socially conditioned details such as fad vocabulary and some aspects of intonation. But the main features will stick.

And to really get a sense of what the future will sound like, listen to young women. They're usually the leaders in language change, and the accent you hear young women speaking with now is the accent you'll hear them speaking with when they're older.

Here, listen to Brooke Shields in 1980, at age 15:

Now listen to her last year, at age 49:

A few changes, but mostly just intonation and tone.

So today's young people will still sound the same in 2050 as middle-aged people. And what do today's young people sound like? Have a listen to Abigail Breslin, 18 years old when she did this interview last fall:

Now, Abigail Breslin was born and raised in New York City, just like Brooke Shields. How much has changed between generations? Their accents are pretty similar (and not stereotypical "New Yawk" accents either), but there are a few little shifts: for example, Breslin's "-ing" has moved towards "-eng"; the vowel in "much" is lower, towards "mahch"; the "-tion" in words like "organization" is more towards "shen."

So, continuing in that direction, what will a 20-year-old of 2050 sound like? If she's from New York and a reasonably well-off family, like Shields and Breslin, the vowels may have shifted even a little farther in the same directions, which to us might sound more "relaxed." The same may be true in some other parts of the U.S. as well… But not everywhere.

You might think that TV and movies and the general mobility of the population would mean accents are getting more and more similar across the country. This turns out not to be the case. Kids don't learn their accents from TV; they learn them from the people around them. And different regions are in some ways becoming more different from each other.

Thanks to detailed research done by many linguists (such as in the Atlas of North American English by William Labov, Sharon Ash, and Charles Boberg), we have a good picture of what's been going on in American English. Some parts of the U.S. are going through gradual but identifiable shifts of vowel sounds right now. For instance, in much of the country, the "oo" sound — as in "loop" — is moving forward in the mouth, towards "ew."

The cities near the Great Lakes are well progressed in what linguists call the Northern Cities Shift — "on" is sounding more like "an" used to and "Ann" is sounding more like "Ian." Meanwhile, "bet" is moving towards "but," and "ow" as in "out" is also moving farther backward in the mouth — which is the opposite of what's happening farther south, where "out" is moving towards "at."

Also in the South, the "ar" sound as in "barn" is moving towards "or" as in "born. Some other elements of the accent — such as "side" sounding more like "sad" — are also getting stronger, not weaker. On the other hand, though Southerners and New Yorkers alike are known for dropping "r" after vowels, that's becoming less prominent — younger speakers are mostly keeping the "r."

Over on the West Coast, linguists such as Stanford's Penelope Eckert have found that in some parts of California, vowels are tending to shift in the opposite direction from those near the Great Lakes: for example, "bit" is moving towards "bet," "bet" is moving towards "bat," and "hat" is moving towards "hot." This is similar to what we're hearing between Brooke Shields and Abigail Breslin, but there are some differences — Californian front vowels are moving up before nasal consonants: "ing" is moving towards "eeng" and "and" is becoming more like "ee-and."

Those are just some representative examples. There are also changes of these kinds happening in other dialects of American English. Socioeconomic levels and ethnic groups make an important difference in accent and dialect, and shifts in identity can lead to shifts in accent. There's a lot more going on than the few details I've mentioned. But it's generally gradual. And it's not all becoming the same.

But what about grammar? Vocabulary? Will texting and Twitter and other social media change the way we use English?

Twitter, texting, and web articles are all new genres (though there are several types of web article), and they have their own developing styles — which don't have any great bearing on other genres. Every genre of writing — from business letters to mystery novels — has its own stylistic tendencies. They change slowly; as linguists such as Douglas Biber have found, most genres of written text have been getting gradually less formal over the last couple of centuries, largely because of trends in literacy and democratization. But genres don't necessarily have a strong influence on other genres; the way you write a business letter doesn't have much to do with how you Tweet or blog.

And changes in the grammar we use in standard English? That's a kind of change that takes place over centuries. But there are a few things we can expect to be more fully advanced than they are now.

We're using noun modifiers in place of adjectives more now — California drought rather than Californian drought or politics blog rather than political blog — and we can expect that to continue. The more we do this, though, the more we need to use other ways to keep the meaning clear. We may become even more strict about word order. We may actually pronounce some punctuation — "slash" is already being used as a conjunction, as Anne Curzan has pointed out: "my sister slash best friend."

But we will certainly continue to convert words from one grammatical role to another: changing nouns to verbs ("Let's green-light that"), verbs to nouns ("That's the ask"), and so forth. Such conversions have always been common in English and aren't going to stop anytime soon.

What kinds of words will people be using in 2050? The fad words of today will not be the fad words of 2050. But many words that are fad words at one time are socially acceptable words later on, as the people who used them when young keep using them when older: cool to mean "good" went from faddish in the 1950s and '60s to entirely acceptable, if informal, by the 1990s; chill out to mean "relax" has traced the same course starting a couple of decades later. Many fad words from 35 years ago have gone out of style, totally rad though they may have been at the time, but the ones that have stuck have become commonplace. So there will be words that annoy you now that will be less annoying to people in 2050. Expect impactful and incent to be unremarkable, and sick to be an accepted informal equivalent of cool. Sorry!

Do I have any idea what the new slang words will be in 2050? No, and you can safely ignore anyone who claims to. Really, did any of you who were around in 1980 foresee today's slang fads?

So, then… how much does American English shift in 35 years? Have a listen to these ads from 1980 — as many of them as you can take:

We can see that the acting style and the ad production values (and use of music!) have changed noticeably between then and now. But how much have the words they use and the accents they speak with changed? If you want a huge change in those, you'll need to wait longer than 35 years. The intonation curves seem to have shifted, but much of that is the difference in acting styles. Watch a clip from Johnny Carson in 1980 and tell me they're speaking much differently:

The one thing I am most sure of, though, is that singular they ("Everyone can do what they want") will be common, accepted standard English, resisted by only a small minority of people. It's already increasingly endorsed by authorities and widely accepted by editors.

Themself will also be an unremarkable word that your computer's spell-checker won't change to themselves. And in order to make a clear distinction between singular and plural, expect to see informal super-plural forms showing up like they-all. After all, we already went through this once centuries ago with thou and you!