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.

I am interested in the culture of China.

He is good at reading Chinese text.

I am busy with work during the day.

I work during the daytime.

He is researching the functions of the midbrain.

He was watching the television relay.