What is diphthong definition?

A diphthong is a combination of two vowel sounds in one syllable where the sound starts as one vowel and then glides towards another vowel sound in the same syllable. Diphthongs are pronounced as one sound, but they still have two distinct vowel sounds within them. The English language has a number of diphthongs, such as the "ai" in "pain" and the "oi" in "coin." Diphthongs can also be written using two vowel letters, such as "ou" in "house" or "ai" in "aim." They are important in language learning as they can change the meaning of words and affect the rhythm and melody of speech.