He is conducting research on the radula of mollusks.

He is doing special exercises to strengthen his tongue muscle.

He was diagnosed with tongue cancer.

In Sanskrit phonology, retroflex sounds play an important role.

Back vowels are vowels that are pronounced using the back of the tongue.

A back vowel is a sound where the back of the tongue approaches the palate.

Retroflex sounds are difficult to pronounce.

A coronal is a sound that is pronounced using the tip or the upper part of the tongue.

Retroflex is a phonetic feature that does not exist in Japanese.

A dorsal sound is a sound that is pronounced by the back of the tongue approaching or touching the palate or pharynx.