Voiceless TH vs S

think vs sink: hear and say the difference

think and sink are identical except for one sound: think has the voiceless th, /θ/, and sink has the s sound, /s/. For TH the tongue tip comes forward to the teeth — you can see it — while for S it stays behind them near the ridge; TH is soft and spread, S is a thin, sharp hiss.

Listen

The two words

think

/θɪŋk/

the voiceless th

sink

/sɪŋk/

the s sound
Articulation

The difference

What actually changes

For TH the tongue tip comes forward to the teeth — you can see it — while for S it stays behind them near the ridge; TH is soft and spread, S is a thin, sharp hiss.

think — /θ/

In the mouth
Lips
Relaxed and slightly apart — they must not close.
Tongue
Tip just touching, or peeking between, the front teeth.
Jaw
Slightly open so the tongue can reach the teeth.
Tongue and lips

sink — /s/

In the mouth
Lips
Slightly spread, corners back.
Tongue
Tip near — not touching — the ridge, with a narrow groove down the middle.
Jaw
Almost closed; the teeth nearly meet.
Tongue and lips
In context

Each word in a sentence

  • think

    I think we should wait.

  • sink

    The dishes are in the sink.

Who merges this

Why this pair is hard

Mandarin, Japanese, Korean, French, German and Russian have no TH and reach for S, which is exactly what makes this the pair to drill. European Spanish and Modern Standard Arabic have the TH sound already, so for those speakers the work is only in the English words that use it.

Questions

Straight answers

What is the difference between "think" and "sink"?

One sound. think is /θɪŋk/ and sink is /sɪŋk/ — everything else in the two words is identical, so that single contrast carries the whole meaning. For TH the tongue tip comes forward to the teeth — you can see it — while for S it stays behind them near the ridge; TH is soft and spread, S is a thin, sharp hiss.

Why do I say "think" and "sink" the same way?

Mandarin, Japanese, Korean, French, German and Russian have no TH and reach for S, which is exactly what makes this the pair to drill. European Spanish and Modern Standard Arabic have the TH sound already, so for those speakers the work is only in the English words that use it.

Should I train my ear or my mouth first?

Your ear. If you cannot reliably hear which word was said, your mouth has no target to aim at, and drilling produces a sound you cannot check. Run the listening test on this page until you are scoring four or five out of five, then record the pair.

Practise this word

Say "think" and "sink" and see which one you said

One take covers both words: reference mode aligns each sound against its target, so the contrast comes back scored on both sides. Free, private, in your browser.