The digraph th represents a dental consonant and corresponds to two different sounds, respectively voiceless and voiced.
The dental sounds are:
th (/θ/): thing, think, three;
th (/ð/): father, that, the.
To pronounce the dental diagraph th the tongue passes through the teeth.
- th (/θ/): voiceless, vocal cords do not vibrate to produce the sound;
- th (/ð/): voiced, vocal cords vibrate to produce the sound.