What does adelphia mean in Greek?

There isn't a word "adelphia" in standard Ancient or Modern Greek that has a commonly understood meaning. It's possible:

* It's a misspelling: Perhaps it's a misspelling of a similar-sounding Greek word. Could you double-check the spelling?

* It's a proper noun: It might be a place name, a family name, or a name created for a specific purpose (like a business or organization).

* It's a neologism or coinage: Someone may have invented the word.

Without more context, it's impossible to determine its meaning.