1) simple, single
3) good fulfilling its office, sound
3a) of the eye
Part of Speech: adjective
Citing in TDNT: 1:386, 65
Probably from G1 (as a particle of union) and the base of G4120; properly folded together, that is, single (figuratively clear): - single.
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 ἁπλοῦς; click on the second column to search for that grammatical form of the root ἁπλοῦς; click on the third column to search for that word and grammatical form; click on the total to search for the root ἁπλοῦς.