1. “-in” and “-ing” have different nasal endings. For the sound “-in”, its production should be ended with the tip of the tongue placed against the teeth ridge while the roof of the mouth should be touched by the root of the tongue when making the sound “-ing” . Both sounds are produced with the air releasing from the nose.

2. The difference between them is that the jaw is more lowered for the sound “-ing” than for “-in”. the lips are spreading tightly in “-in” , but less so for “-ing”.