/θ/

Place the tip of your tongue lightly between your upper and lower front teeth, so it just barely peeks out. Keep your tongue flat and relaxed. Now gently blow air over your tongue and through the gap between your tongue and teeth. You should feel a soft, continuous stream of air escaping with light friction.

Here's the key: your vocal cords stay silent. If you put your hand on your throat, you shouldn't feel any vibration. The sound is just air and friction.

Many learners substitute /θ/ with similar sounds from their native language:

• Saying /t/ instead: "tink" for "think" - your tongue is stopping the air completely instead of letting it flow through
• Saying /s/ instead: "sink" for "think" - your tongue is too far back and creating a hissing sound
• Saying /f/ instead: "fink" for "think" - you're using your lip against your teeth instead of your tongue

Try the "finger test": hold a finger about an inch in front of your mouth. You should feel a gentle, broad stream of air when you make /θ/ correctly. If you feel a sharp burst (that's /t/) or a thin, focused hiss (that's /s/), adjust your tongue position.

A helpful trick: start by saying /f/, then slowly slide your tongue forward to replace your lower lip. When your tongue tip pokes between your teeth, you've found /θ/.