Voiced and Unvoiced Consonants

In my pronunciation chart, I say that for the diphthongs αυ, ευ, and ηυ, the υ takes a "v" sound before vowels and voiced consonants, and an "f" sound elsewhere.

To clarify, "voiced" consonants are those which make a sound when you pronounce them, versus "unvoiced" consonants that are like a whispered sound. E.g., our English "b" is a voiced consonant, as in the word "bee"; its "unvoiced" form is our letter "p," as in the word "pea." Say "buh"and "puh" and you'll see that your mouth and lips form the same shape, but you "hear" the "b" in "buh," but don't "hear" the "p" in "puh" – hence, "p" is "unvoiced."

Thus, the voiced consonants are: β γ δ ζ λ μ ν ρ (and the rare times σ/ς is pronounced like a "z").

The unvoiced consonants are: θ κ ξ π σ/ς τ φ χ ψ

I also say that γ is a "y" (as in "yes") sound before vowels or diphthongs that are pronounced as either "ee" or "eh," and a "gh" sound elsewhere.

The "ee" vowels and diphthongs are: η ι υ ει οι

The "eh" vowels and diphthongs are: ε αι

The above is for the Historical Pronunciation of Greek (i.e., the Modern Greek Pronunciation), which has an overabundance of "ee" sounds due to what's called "itacism," the mixing up of Greek historical spellings because the underlying vowel phonemes (sounds) had merged with the sound of ι.

Though Buth's Phonemic Koine Greek (again, see my pronunciation chart) pronounces η as "ey" in "obey," and υ and οι as a French u, instead of all three as "ee" as above, a γ that precedes them - or, more specifically, that precedes the "front" vowels ι ει η ε αι (formed with the tongue in a front position) - is also to be pronounced closer to a "y" sound. On the CDs, though, Buth seems to use "gh" for all instances of γ, as I've also heard some Greeks do, and Lydia said that her Greek-speaking priest wants her to pronounce γ as a "gh" and not as a "y," so pronouncing γ as "gh" in almost all instances may be fine.