1) if, whether
Part of Speech: conjunction
A primary particle of conditionality; if, whether, that, etc.: - forasmuch as, if, that, ([al-]) though, whether. Often used in connection or composition with other particles, especially as in G1489, G1490, G1499, G1508, G1509, G1512, G1513, G1536, and G1537. See also G1437.
|(εἰ τύχοι) probably||71.13|
|(εἰ μή) except that||89.131|
|c that, whether||90.26|
|(εἰ μήν) surely||91.8|
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 εἰ; click on the second column to search for that grammatical form of the root εἰ; click on the third column to search for that word and grammatical form; click on the total to search for the root εἰ.