Front vowels are pronounced using the front part of the tongue.

A front vowel is a vowel that is articulated with the front part of the tongue.

He stuck out his tongue and licked the ice cream.

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

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

A central vowel is a vowel that is pronounced in the central part of the tongue.

The central vowels in Japanese are 'a', 'e', 'o'.

In this old document, the usage of vowels is different from today.

He stuck out his tongue and licked the ice cream.

The nucleus is the central part of a syllable in phonetics.