1) when now, since now
1a) of time: when now, after that
1b) of cause: since, seeing that, forasmuch as
Part of Speech: conjunction
From G1893 and G1211; since now, that is, (of time) when, or (of cause) whereas: - after that, because, for, (that, -asmuch as), seeing, since.
These two sites give similar information, with the definition from several dictionaries and statistics on the use of the word.
Perseus Digital Library
University of Chicago's Logion lexicon
Thayer's dictionary plus other information.
From this site's dictionary (in Italian)
Click on the first column to search for that word as a form of the root ἐπειδή; click on the second column to search for that grammatical form of the root ἐπειδή; click on the third column to search for that word and grammatical form; click on the total to search for the root ἐπειδή.