"Diphthongs are indicated by combinations of hooks and circles"

In this quote, John Robert Gregg is referring to a linguistic principle known as diphthongs. Diphthongs are a type of vowel sound that is developed by integrating two different vowel sounds together. Gregg describes that these diphthongs can be recognized by using a mix of hooks and circles. These signs are typically utilized in phonetic transcription to represent particular sounds. The hooks and circles serve as visual indications of the unique noise created by the mix of two vowels. This quote highlights the importance of accurately representing diphthongs in written language, as they can significantly affect the meaning and pronunciation of words.