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

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.

The Great Vowel Shift played a significant role in the history of English.

He is writing a thesis on the octovocalic theory.

A diphthong refers to the phenomenon where two vowels are pronounced consecutively within a single syllable.

The failure of the project was due to a situation where too many cooks spoil the broth.

I have been to El Salvador.