1. The words "sin" and "sing" both share a similar ending sound to the Chinese character "恩". 2. The first word "sin" phonetically sounds like "en" with the tip of the tongue against the alveolar ridge (the area behind the upper front teeth). 3. In the second word "sing", the tongue position differs from the first. The tip of the tongue presses against the lower gum and the back of the tongue pushes up against the soft palate. The mouth should be opened wide.