What are the rules of gender determination in Greek? I have looked but cannot get a definite answer.
Search for gender NEAR determine in your Lexicons and Grammars (with Match all forms). Use a dynamic collection type:(lexicon,grammar) instead of specifying books.
There does not appear to be a definite answer.
For Indo-European languages, the normal answer is:
What are the rules of gender determination
2 other users mentioned a lack of definiteness.
grammatical gender is like "how may licks to the center of a Tootsie Pop?" The world may never know. I remember as a middle school student in Spanish I being told Pen (la pluma - fem), Pencil (el lapiz - masc) and Paper (el papel - masc.) are exhibit 1 of grammatical gender being totally unrelated to biological gender.
If you're asking what reasoning the ancient Greeks used to decide whether a noun in their language would be masculine, feminine, or neuter, the answer is "we don't know." As others have pointed out, though, in the Greek language gender is a grammatical category. It has no bearing on meaning that I am aware of.