1) that which is the cause of anything resides, causative, causing
1a) the author
1a1) of a cause
1a2) of crime or offence
Part of Speech: adjective
From the same as G154; causative, that is, (concretely) a causer: - author.
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 αἴτιος; click on the second column to search for that grammatical form of the root αἴτιος; click on the third column to search for that word and grammatical form; click on the total to search for the root αἴτιος.