1) to be useful, to profit, help
2) to receive profit or advantage, be helped [or have joy]
Part of Speech: verb
A prolonged form of an apparent primary verb ὄνομαι onomai; for which another prolonged form ὀνάω onaô is used as an alternate in some tenses (unless indeed it be identical with the base of G3686 through the idea of notoriety); to gratify, that is, (middle voice) to derive pleasure or advantage from: - have joy.
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 ὀνίνημι; click on the second column to search for that grammatical form of the root ὀνίνημι; click on the third column to search for that word and grammatical form; click on the total to search for the root ὀνίνημι.