Some people wrongly pronounce the voiceless th as an s. They say sank and thank the same way. They also tend to wrongly pronounce the voiced th as a z. They say breeze and breathe the same way. Again, the mistake lies in the position of the tongue. For the s and z, there is also air passing through the tip of the tongue, but the tongue is not touching the teeth. It is touching a little bit behind, on the gum ridge. Pay attention to these tongue positions shown in the illustrations below as you do the following exercises.