Consonants
Consonants are categorized by quality. The consonants within each category tend to have certain characteristic behaviors in certain situations. When followed by a given letter, the consonants in one category may combine with it. The consonants in another category may tend to be replaced when followed by a given letter. You will often come across references to these categories. The table below is based on one found in Greek Grammar by James Hadley, revised by Frederic de Forest Allen, p. 8.
Mutes
Mutes are those consonants that are pronounced with a stoppage of the breath. Some have no vocalization at all, e.g., the breathed consonants π, τ, and κ. Others, β, δ, and γ, are voiced. Still, there is that stoppage. Early on, the rough mutes were aspirates, apparently pronounced as a combination of a stopped consonant and an “h” sound. Although it is thought that the sound of these rough mutes softened in Hellenistic Greek, they are still categorized among the mutes. The following matrix shows the categorization of mutes into three classes and three orders.
* Also called dental mutes
** Also called gutteral mutes