The seventeen consonants are divided into stops (or mutes), spirants, liquids, nasals, and double consonants. They may be arranged according to the degree of tension or slackness of the vocal chords in sounding them, as follows:
a. Voiced (sonant, i.e. sounding) consonants are produced when the vocal chords vibrate. The sounds are represented by the letters β, δ, γ (stops), λ, ρ (liquids), μ, ν, γ-nasal ( cross19 a) (nasals), and ζ. (All the vowels are voiced.) ρ with the rough breathing is voiceless.
b. Voiceless (surd, i.e. hushed) consonants require no exertion of the vocal chords. These are π, τ, κ, φ, θ, χ (stops), ς (spirant or sibilant), and ψ and ξ.
c. Arranged according to the increasing degree of noise, nearest to the vowels are the nasals, in sounding which the air escapes without friction through the nose; next come the semivowels w and y ( cross20 a), the liquids, and the spirant ς, in
sounding which the air escapes with friction through the cavity of the mouth; next come the stops, which are produced by a removal of an obstruction; and finally the double consonants.
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].