Strong's G1490 — εἰ δε μή (conjunction)
ei de me (ei deh may') (or sometimes ei de mege) conj.
1. but if not
[from G1487, G1161, and G3361 (sometimes with G1065 added)]
KJV: (or) else, if (not, otherwise), otherwise 
Root(s): G1487, G1161, G3361, G1065 
Hebrew root: δέ