Put your tongue tip lightly against the bottom edge of your top front teeth and push air through the gap. That hiss is the first TH, the one in think. Now make the same shape with your voice switched on, so the gap buzzes instead of hisses. That’s the second TH, the one in this. Two different sounds, written with the same two letters, and very few languages besides English ask your tongue to make either of them.
So your mouth does what every mouth does with an unfamiliar sound. It reaches for the nearest thing it already owns. Think comes out as sink, or fink, or tink. This comes out as dis or zis. Which substitute you reach for is one of the most reliable signs of where you learned to speak. A phonetician can often name your first language from your TH alone, before you’ve finished the sentence.
The good news hiding in that is simple. The TH sound isn’t hard to make. It’s just foreign to your mouth. There’s no strength involved, no trick of timing. The tongue only has to learn to sit a few millimeters forward of where it has spent your whole life keeping it.
TH is two sounds wearing one spelling: the voiceless /θ/ in think, math, three, and the voiced /ð/ in this, mother, breathe. The mouth position is identical for both. The only difference is whether your vocal cords are running, the same voiced-voiceless split you already know from /s/ versus /z/. The sound is unfamiliar rather than difficult: very few languages use it, so most learners replace it with the closest sound their first language already has (/s/, /f/, /t/, /d/, or /z/). Fixing it is mostly about getting your tongue used to a position it has been avoiding, and the mirror does most of the teaching.
What the two TH sounds actually are
Both TH sounds are made the same way. The tip of the tongue rests against the bottom edge of the upper front teeth, or peeks just slightly between the teeth, and air flows out over the top of the tongue through the narrow gap. Phoneticians call this a dental fricative: dental for the teeth, fricative for the friction of air squeezing through.
The two sounds differ in one thing only. For /θ/, the voiceless TH in think, the vocal cords stay open and you hear only the hiss of air. For /ð/, the voiced TH in this, the vocal cords vibrate and the hiss turns into a buzz. Put two fingers on your throat and switch between them: think, this, think, this. The buzz you feel on this is the voicing, and it’s the whole difference.
This is the same pairing you already use without thinking. /s/ and /z/ are one mouth position with the voice off and on. So are /f/ and /v/, and /t/ and /d/. The voiceless and voiced TH are just another such pair, sharing the dental position. If you can already say Sue and zoo, you already control the only variable that separates the two TH sounds.
A handful of English words exist as voiced-voiceless pairs spelled almost identically, which is the cleanest way to hear the contrast:
| Voiceless /θ/ | Voiced /ð/ | What changed |
|---|---|---|
| breath (the noun) | breathe (the verb) | the verb buzzes, and the vowel shifts (eh → ee) |
| bath (noun) | bathe (verb) | the verb adds voice and changes the vowel |
| mouth (noun) | mouth (verb, “to mouth words”) | same spelling, voiced when it’s the verb |
| cloth (noun) | clothe (verb) | the verb voices the TH |
One spelling, two sounds: which is which
The spelling never tells you whether a TH is voiced or voiceless. Thigh and thy rhyme and both open with TH, yet one hisses and one buzzes. But the distribution isn’t random, and a few reliable patterns cover almost every word you’ll meet.
Grammar words that start with TH are voiced (/ð/). The small structural words that point and connect (the, this, that, these, those, they, them, their, there, then, than, though) all buzz. This is the highest-yield pattern to learn, because these words are the most frequent words in the language. Get the voiced TH onto the and they and you’ve fixed thousands of TH sounds a day in one move.
Content words that start with TH are voiceless (/θ/). Nouns, verbs, and adjectives that begin with TH hiss: think, thing, three, thank, thin, thick, thought, through, thumb, Thursday.
TH at the end of a word, spelled -th, is usually voiceless (/θ/): bath, math, both, mouth (the noun), teeth, path. But when the word ends in a silent -e (-the), it’s voiced: breathe, bathe, clothe. One word breaks the pattern worth memorizing: smooth ends in plain -th but still buzzes.
TH in the middle of a word is the messy case. Common everyday words, mostly old Germanic ones, take the voiced TH: mother, brother, weather, other, rather, together, either. Words borrowed from Greek or Latin take the voiceless TH (author, method, sympathy), and so do native words built on a voiceless-TH root: nothing and something (from thing), healthy (from health), birthday (from birth).
| Position | Voicing | Examples |
|---|---|---|
| Grammar word, initial | voiced /ð/ | the, this, that, they, them, there, then, than, those, these, though |
| Content word, initial | voiceless /θ/ | think, three, thank, thing, thin, thick, thought, thumb, Thursday |
| Final, spelled -th | voiceless /θ/ | bath, math, both, mouth, teeth, path, month, fourth, truth |
| Final, spelled -the | voiced /ð/ | breathe, bathe, clothe, soothe (plus smooth, a plain -th exception) |
| Medial, Germanic | voiced /ð/ | mother, father, brother, weather, other, together, rather |
| Medial, borrowed or built on a /θ/ root | voiceless /θ/ | author, method, sympathy (borrowed); nothing, healthy, birthday (native, from thing / health / birth) |
A few words genuinely vary between speakers. With is /wɪθ/ (voiceless) for many Americans and /wɪð/ (voiced) for others, and both are standard. Don’t lose sleep over the handful of words that float between the two. The patterns above will steer you right on the overwhelming majority.
How to make the sound
If your first language doesn’t have the dental fricative, here’s the path from nothing to a usable TH:
- Find the contact point. Rest the tip of your tongue against the bottom edge of your upper front teeth. Not the gum behind them, the teeth themselves. A little of the tongue tip can show between the teeth. This visibility is the point: TH is one of the few English sounds you can watch yourself make.
- Blow, don’t push. Keep the tongue soft and let air flow out over it through the gap. You should hear a quiet, steady hiss, lighter and “flatter” than an /s/. That’s the voiceless /θ/. Hold it for two seconds so your mouth memorizes the position.
- Add the buzz. Keep everything exactly where it is and turn your voice on. The hiss becomes a buzz. That’s the voiced /ð/. Switch back and forth, /θ/ to /ð/, without moving your tongue, only your voice.
- Attach a vowel. Try thee, thaw, though for the voiced one, think, thin, thumb for the voiceless one. Keep watching the mirror. The tongue should reappear at the teeth on every TH.
- Put it in a word, then a phrase. I think so. This one. Both of them.
Three errors account for almost every TH that comes out wrong. If you pull the tongue back behind the teeth, you get an /s/ or a /t/: think becomes sink or tink. If you bring your bottom lip up to the teeth instead of your tongue, you get an /f/ or a /v/: think becomes fink. And if you press the tongue too hard and stop the air completely, the fricative turns into a stop and you get a /d/: this becomes dis. The mirror catches all three, because in every one of them the tongue tip has disappeared from view. If you can see a sliver of tongue at your teeth, you’re making a real TH.
What your first language reaches for instead
When a sound doesn’t exist in your first language, your mouth substitutes the closest one it has, and it does this so consistently that the substitution becomes a signature. None of these are deficiencies — they’re just the nearest neighbor your language handed you. Find your starting point below.
| Your L1 | think /θ/ tends to become | this /ð/ tends to become | What to work on |
|---|---|---|---|
| Mandarin Chinese | sink (/s/) | dis (/d/) | The tongue is sitting behind the teeth for the /s/. Move it forward to the teeth. See the Chinese-speaker mistakes guide for the fuller picture. |
| Cantonese | free / fink (/f/) | dis (/d/) | The lip is coming up to the teeth instead of the tongue. Keep the lip down; lead with the tongue. |
| Japanese | sink (/s/) | zis (/z/) | Same as Mandarin: tongue forward, off the ridge and onto the teeth. |
| Korean | sink (often a tense /s/) | dis (/d/) | Soften the contact and let air through; don’t let the TH harden into a stop. |
| French | sink (/s/) | zis (/z/) | The sounds feel “imprecise” to a French ear; let them be slightly soft. Tongue to the teeth, not behind. |
| German | sink (/s/) | dis / zis | German has no dental fricative at all; build both from the mirror drill above. |
| Spanish (Latin American) | tink / sink | dis (/d/) | You already make something very close to the voiced TH inside words like lado and nada, where your d softens almost into it. Tighten it into a buzz and carry it to the start of this and that. |
| Brazilian Portuguese | tink / fink | dis (/d/) | Lead with the tongue at the teeth and keep air flowing instead of stopping it into a t or d. |
| Hindi, Tamil | tink (a dental t, with a puff in Hindi) | dis (a dental d) | Your t and d are already at the teeth, which is half the battle. Loosen the contact so air leaks through into a fricative instead of a clean stop. |
| Russian | tink / sink | dis / zis | A /t/ or /s/ (and sometimes a lip-teeth /f/) stands in. Put the tongue on the teeth and let it hiss instead. |
| Thai, Vietnamese | tink (/t/) | dis (/d/) | The “th” in your romanization is an aspirated t, not this sound. Trade the stop for an open, hissing tongue. |
A few first languages give you a head start. Arabic has both TH sounds as full letters (ث for /θ/, ذ for /ð/), so most Arabic speakers already produce them and only need to keep them from drifting toward /s/ and /z/ in fast English. Castilian (European) Spanish uses /θ/ natively (the c in gracias and cinco is exactly the voiceless TH), so those speakers own half the pair already. Greek has both. If your language is on this short list, your work is placement and consistency, not building the sound from scratch.
Which substitutions cause real confusion
Here’s the honest part most guides skip. Many TH substitutions never cause a real misunderstanding. If you say I sink so, no American pictures a kitchen sink; context does the work, and the conversation moves on. Substituting the voiced /ð/ with a d on function words, the becoming duh and this becoming dis, almost never blocks meaning either, because those words are so predictable from grammar alone.
What that means is that you can prioritize. A few substitutions do collide with real words and are worth fixing first:
| You mean | But it can sound like |
|---|---|
| think | sink |
| thing | sing |
| three | free / tree |
| thought | fought / taught |
| thin | fin / sin |
| math | mass |
| path | pass |
| mouth | mouse |
These are the ones where the wrong tongue position changes the word, so the voiceless /θ/ in content words is where intelligibility lives. The voiced /ð/ on function words rarely confuses anyone, but because those words are everywhere, getting the TH right on the, this, and they is the single biggest change in how native you sound, even when it changes nothing about whether you’re understood. If you only have the patience for one, fix the voiceless /θ/ for clarity. If you want both clarity and the native texture, the function words are the higher-leverage half. (For the longer view on what “sounding native” is and isn’t worth, see ‘Lose Your Accent’? You’re Asking the Wrong Question.)
Practice phrases
Read each line out loud, twice. Every line is loaded with both TH sounds. In the respellings, th marks the hissed sound (as in think) and dh the buzzed one (as in this); capitals mark the stressed syllable. Watch the mirror on the first pass and listen on the second.
- I think this is the third one. I THINK DHiss iz dhuh THURD wun.
- They both have the same mother. DHay BOTH hav dhuh same MUDHer.
- Thanks for the other three. THANKS fer dhee UDHer THREE.
- Is this the path to the bathroom? Iz DHiss dhuh PATH tuh dhuh BATH-room?
- The weather's worse than they thought. Dhuh WEDHerz WURS dhuhn DHay THAWT.
- Both brothers think the same thing. BOTH BRUDHerz THINK dhuh SAME THING.
- Take a deep breath, then breathe out. Take uh DEEP BRETH, dhen BREEDH out.
- Thirty-three thousand. THUR-tee THREE THOU-zuhnd.
- There's nothing wrong with that. DHairz NUTH-ing RAWNG with DHAT.
- I'd rather do this together. Ide RADHer doo dhiss tuh-GEDHer.
The breath/breathe line is the one to slow down on: breath hisses, breathe buzzes, and the vowel shifts from eh to ee right along with it.
Where to hear it clearly
You don’t have to hunt for TH in American speech. A few situations put so many in a row that your ear can lock onto the sound:
- Anyone saying numbers
Three, thirteen, thirty, thousand, fourth, fifth, sixth. Prices, dates, scores, phone numbers, and addresses are full of voiceless /θ/. Listen to a sportscaster read a score or a cashier read a total and count the TH sounds.
- The word 'the'
The is the most frequent word in English, and it carries the voiced /ð/ every single time. A news anchor says it hundreds of times an hour, crisply. Pick one sentence from a broadcast and notice that the the never turns into a duh.
- 'Thank you' and 'I think'
Two of the most common phrases in spoken English open on a voiceless /θ/. They’re said so often, and so casually, that they’re a perfect model for how light the sound is meant to be. Native speakers barely touch the teeth.
- Days and dates
Thursday, the third, the thirtieth, this month. Any time someone schedules something out loud, the TH sounds stack up. Calendars are a TH drill in disguise.
- The function-word stream
This, that, these, those, they, them, there, then. Ordinary conversation runs on these words, and every one of them buzzes. Once your ear catches the voiced TH in the small words, you start hearing it everywhere.
Pick one of these, listen for sixty seconds, and count the TH sounds you catch. Most learners reach fifteen or twenty without trying. After a week of this, the TH stops being a sound you have to remember to make and starts being one your ear expects.
FAQ
The mouth position is identical for both: the tongue tip rests against the upper front teeth and air flows through the gap. The only difference is the voice. The voiceless TH /θ/, as in think and math, is just the hiss of air. The voiced TH /ð/, as in this and mother, adds vocal-cord vibration so the hiss becomes a buzz. It’s the same on-off voicing that separates /s/ from /z/. See the voiceless-versus-voiced TH comparison for the side-by-side.
The dental fricative is rare among the world’s languages. It asks the tongue to sit between or against the teeth and leak air, a position most languages never use, and it’s also one of the last sounds children acquire even in English. It’s also acoustically faint and easy to mishear, which is why languages that once had it have tended to merge it into louder, more stable neighbors like /t/, /d/, /f/, or /s/ over the centuries (German and Dutch, for instance, merged it into /d/). The result is that learners from most first languages have simply never made the sound and have to add it.
You’ll usually still be understood, because context fills the gap and listeners rarely confuse I think so with I sink so. A handful of substitutions do collide with real words (think/sink, three/free, thought/fought), and those are worth fixing for clarity. Replacing the voiced TH with a d on words like the and this rarely causes confusion, but it’s the strongest single marker of a non-native accent because those words are so frequent.
Use the position. Grammar words starting with TH are voiced (the, this, that, they, them, there). Content words starting with TH are voiceless (think, three, thank, thing). A TH at the end spelled -th is usually voiceless (bath, math, both), while one spelled -the is voiced (breathe, bathe, soothe); the one common exception is smooth, which is plain -th but still buzzes. Medial TH in old everyday words is voiced (mother, weather, other); in Greek and Latin borrowings it’s voiceless (author, method, sympathy), as are native words built on a voiceless root like nothing (from thing).
Because you’re bringing your bottom lip up to your top teeth, which is how you make an /f/, instead of bringing your tongue to your teeth. This is common for Cantonese and some Russian speakers, where three becomes free and think becomes fink. The fix is to keep the lip down and lead with the tongue. Watch a mirror: for a real TH you should see the tongue tip at the teeth, not the lip.
Producing the sound in isolation takes minutes once you find the tongue position in a mirror. Producing it automatically in fast speech, without slipping back to your old substitution, usually takes a few weeks of daily practice. The slow part isn’t the sound itself but retraining the reflex, since your mouth has spent years routing around a position it never needed.
Stand in front of a mirror and say think, then this. If you can see a sliver of your tongue at your teeth on both, you’re already making the sound; the rest is repetition until you stop having to think about it. Start with the voiceless /θ/ in the words that would otherwise collide with real ones, then bring the voiced /ð/ to the and they and watch how much of the work that one move does. You’ll pick this position up faster than most English sounds, for the simple reason that you can watch yourself do it.
