The Two TH Sounds in English: /θ/ vs /ð/

English uses the same two letters, “th”, for two completely different sounds: the quiet one in think /θɪŋk/ and the buzzing one in this /ðɪs/. In IPA they get separate symbols, θ for the voiceless sound and ð for the voiced one, so there is no more guessing. Type both words into the pronunciation Studio, play them back to back, and the difference is impossible to miss.

The good news is that your tongue does exactly the same thing for both. Only one thing changes between them, and once you feel it, you have both sounds.

The one thing that separates them

Put a hand flat on the front of your throat and say a long “sss”, then switch to a long “zzz” without moving your mouth. Your mouth stays put, but “zzz” makes your throat vibrate and “sss” does not. That vibration is voicing, and it is the only difference between the two TH sounds.

/θ/ is the voiceless one, the technical name being a voiceless dental fricative. Your throat is silent and only air comes out, as in think, bath, and three.

/ð/ is the voiced one, a voiced dental fricative. Your vocal cords switch on and add a buzz, as in this, mother, and breathe. Same tongue, same air, voice added.

That word “fricative” simply means the sound is made by squeezing air through a narrow gap until it hisses or buzzes, rather than by fully blocking the air. The two sounds have formal names, the voiceless dental fricative and its voiced partner, if you want the reference detail. It puts the two TH sounds in the same family as /f/, /v/, /s/, and /z/, which are all made the same way. The only thing special about the TH pair is where the gap is: right at the tip of the tongue against the top teeth.

How to make the TH sound, step by step

The sound is physical, so it helps to build it slowly.

1. Place your tongue at your teeth. Rest the tip lightly against the back of your top front teeth, or let it poke just between the top and bottom teeth. Both positions work.
2. Push air across the tip. Breathe out gently so a soft stream of air flows over the tongue. Not a hard burst, just a steady leak.
3. For /θ/, keep your voice off. Make the sound with no voice, like the start of think. A hand on your throat feels nothing.
4. For /ð/, turn your voice on. Keep the tongue exactly where it is and add voice, like the start of this. Now the throat buzzes.
5. Keep it soft. Do not jam the tongue into a hard t or pull it back into an s. The light airflow is what makes it TH.

Common words in each group

Here are everyday words sorted by which TH they use, with IPA and respelling. The voiced group leans heavily on small, frequent words.

Voiceless /θ/, the quiet one:

Voiced /ð/, the buzzing one:

The rough rule for which TH to use

There is a pattern, though it is a tendency rather than a law. Short grammar words, the ones that hold sentences together, usually take the voiced /ð/: the, this, that, these, those, then, there, they, them. Most other words, the ones carrying meaning, take the voiceless /θ/: think, three, thing, thick, thank, bath, math.

It is a useful default when you meet a new word, but it does miss cases, so a dictionary or the Studio is the safe check when a word matters.

Where TH shows up in a word

Both sounds can sit at the start, middle, or end of a word, and hearing them in each position is good practice, because the end position is the one learners drop most often.

The end of a word is where a TH is easiest to lose, because it is quiet and unstressed. Words like bath, month, and fifth need that final /θ/ to stay clear, and breathe, smooth, and with need the final /ð/. Slowing down on the last sound is often all it takes.

When “th” is not a TH sound at all

The two letters “th” do not always spell /θ/ or /ð/. In a small set of names and borrowed words, “th” is simply a /t/ sound, and treating it as a TH would be the wrong move.

These are the exceptions, not the rule, and there are only a handful of them. Still, they are a good reminder that spelling is a rough guide at best, and that the IPA in a dictionary is what actually tells you the sound.

Why so many learners swap the TH sound

A large number of the world’s languages do not have /θ/ or /ð/ at all. When a sound is missing from your first language, your mouth naturally reaches for the closest one it already owns. This is a normal, predictable transfer, not a failure.

The usual substitutions follow clear logic:

• /θ/ becomes /s/ or /t/ or /f/, so think drifts toward sink /sɪŋk/, tink, or fink /fɪŋk/.
• /ð/ becomes /d/ or /z/, so this drifts toward dis or zis.

Every one of these swaps happens because the substitute sound is close in the mouth. Knowing which one you reach for tells you exactly what to adjust: if think comes out as sink, your tongue is a little too far back, so bring the tip forward to the teeth. If it comes out as tink, the tongue is touching too hard and blocking the air, so ease off until the air can flow. Each substitution points to a small, specific fix rather than a vague “try harder”.

Minimal pairs to practise

Minimal pairs are two words that differ by a single sound. They are the best drill for the TH sounds, because they force your ear to hear the contrast.

And here are pairs that target the common substitutions, TH against the sound learners often use instead:

When swapping the TH is not an error at all

It is worth saying plainly: replacing the TH sounds is a standard, respected feature of several English accents. In much of London and southeast England, think is fink and brother is bruvver, a pattern called th-fronting. In parts of Ireland, New York, and the Caribbean, this and that become dis and dat, called th-stopping.

Inside those accents, this is simply how the language is spoken, by millions of people, correctly. None of it is a mistake. You would only change it if you are deliberately aiming for an accent that keeps the TH sounds, and even then it is a choice about which sound you want, not a fix for something broken.

The throat test, one more time

If you remember one thing, make it the hand on the throat. Same tongue at the teeth for both sounds; voice off for /θ/ in think, voice on for /ð/ in this. Everything else follows from that single switch.

Keep the Studio open and play the minimal pairs whenever the two sounds blur together. The voicing switch behind these two sounds runs through the whole consonant system, so the next step is the full guide to voiced and voiceless consonants. If any symbols here are new, how to read IPA starts from the beginning.