How to pronounce Think /θ/ vs Sink /s/ in American English

/θ/

think · three · bath · thin

/s/

sink · see · say · sit

Start here

What separates think /θ/ from sink /s/ is exactly where you place your tongue tip. For /θ/, the tongue tip rests lightly between your upper and lower front teeth while air flows gently over it. For /s/, the tongue tip pulls back behind the teeth, pointing at the bumpy ridge on the roof of your mouth to create a sharp, hissing stream of air. Speakers of French, German, and Japanese often substitute /s/ for /θ/, turning think into sink.

Side by side

How the two sounds differ.

3 small mouth adjustments. Get any one of them wrong and the sound slides into its neighbor.

Dimension

/θ/ Think

/s/ Sink

Tongue tip

Rests lightly between or just behind the upper and lower front teeth.

Pulls back behind the teeth. The front of the tongue creates a narrow groove near the bumpy ridge on the roof of the mouth.

Airflow

Soft and wide. Air flows gently over the flat tongue tip.

Sharp and focused. A narrow groove in the tongue creates a strong hissing sound.

Teeth

Parted just enough to let the tongue peek through.

Close together, nearly touching, keeping the tongue trapped inside.

Try saying

think, thick, thumb, math, path

sink, sick, sum, mass, pass

Now you try.

Record yourself saying "Think" and "Sink" a few times. Listen back — your own ear is the best feedback for nailing the contrast.

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Minimal pairs

Words that change with one sound.

Every pair below differs by exactly one sound: flip /θ/ to /s/ and the meaning flips with it. Tap any word for its full breakdown.

/θ/ Think

/s/ Sink

Why people mix them up

If your ear blurs them, here's why.

The soft TH /θ/ is a rare sound across the world's languages. If your native language doesn't have it, which is true for French, German, Japanese, and many dialects of Spanish, your brain hunts for the closest acoustic match it already knows. For many speakers, that match is /s/. The result: think becomes sink and mouth becomes mouse. /s/ is a high-pressure, hissing sound, while /θ/ is a low-pressure, gentle one. To fix this, you physically need to bring your tongue further forward than feels natural, letting it touch the edges of your front teeth to break the sharp hiss of the /s/.

How to practice

Train the muscle, then the ear.

3 short drills. Do them out loud: feel the change inside your mouth before you try to hear it.

Use a mirror. Say think and physically watch your mouth. You should see the very tip of your tongue peeking between your teeth. If you can't see your tongue, you're probably making an /s/.

The finger test: Hold your index finger vertically against your lips (like a "shh" gesture). Say math. Your tongue tip should gently tap your finger on the TH. Now say mass. Your tongue should stay safely behind your teeth.

Read minimal pairs out loud, focusing on the air pressure: thick / sick, thumb / sum, path / pass. The /s/ should sound sharp and loud, while the /θ/ should sound softer and breathier.

FAQ

Common questions about Think vs Sink.

Why do I sound like I'm saying "sink" when I try to say "think"?

Your tongue is trapped behind your teeth, creating a sharp hiss instead of a soft breath. American English /θ/ requires the tongue tip to physically touch the bottom edges of your upper front teeth, often peeking out slightly. If you keep the tongue pulled back near the roof of your mouth, the air gets squeezed into a tight groove, producing an /s/. Push the tongue forward until it touches the teeth, and the hiss breaks.

Do Americans really stick their tongue out for the TH sound?

Yes, but just a tiny bit. In casual American speech, the tongue tip doesn't stick way out like a lizard. It rests lightly against the bottom edge of the top front teeth, sometimes peeking slightly between the upper and lower teeth. What matters is that the tongue blocks the sharp gap where an /s/ would normally happen. As long as the tongue touches the edges of those front teeth, you get the right soft airflow.

How can I stop my TH from sounding like an S or an F?

By controlling exactly what your breath hits on its way out of your mouth. If your air hits a pulled-back tongue, you get an /s/. If your lower lip touches your top teeth, you get an /f/ (turning think into fink). For a true /θ/, only the tongue tip and the upper front teeth should be doing anything. Keep your lips completely out of the way and let the air flow gently past the tongue.