IPA Greek symbols 1. [i] ι or ει 2. [e] η 3. [ɛ] ε or αι 4. [a] α 5. [o] ο or ω 6. [u] ου 7. [y] υ or οι Tongue Position Chart for Roman Period Koiné front rounded central back high ι,ει υ,οι ου mid η ο,ω mid/low ε,αι ...
There are a number of other patterns and complexities that I could add here. For examples, there is the historical discussion of how the resultative sense developed into the termination sense or how the Greek perfect has always been limited to a smaller set of verbs than the imperfective and ...