vowel contraction ο + ει

I have a vowel contraction table according to which:
ο + ει (gen.) = οι
but
ο + ει (sp.) = ου

Maybe gen.. = general and sp. = special but I still have no idea what they mean.

He enslaves (δουλοῖ) must be an example of the first type(gen.)

Can anybody please explain what gen. and sp. refer to here?

In which book did you find this table?

In Attic-Ionic Greek the dipthong ει may be either genuine (gen.) or spurious (sp.)

The two spurious dipthongs ει and ου are digraphs (two letters representing a single sound) that started to be used around the late fifth century BC to represent long versions of the short vowels ε and ο since Greek at that time had no specific way of representing those two long vowels.

There’s a very good explanation of this in chapter 1 of the Cambridge Grammar of Classical Greek (CGCG) which, if you read it about a half-dozen times, may eventually make sense. At least that’s how long it took for me to understand it :wink:

Thanks a lot, Mitch!
Tico: I didn’t get the vowel contraction table from a book, I found it in a professor’s online course notes a couple months ago (I don’'t remember the references unfortunately). I would be happy to post the table in a Word doc in the Resources section, but I don’t know the posting procedure (or whether there would be any interest).

FWIW vowel contraction in ancient Greek made no sense to me until I learned about vowel height/backness/roundedness and how Greek vowels were positioned on the vowel triangle. All this is covered in chapter 1 of CGCG, and once you know the basics of Greek vowel phonology you can (almost) derive the table of vowel contractions from first principles vs. using (ugh) rote memorization.