(7) The decay of all diphthongs; ai, oi, ei all become a monophthong variously written e and i (rarely ei), as in the dat.
-- Co, ,,,o Oo,,.ei 0.
In final syllables the diphthongs ai, ei, oi, all appear as e.
This many-named and enigmatical tribe was of considerable importance in the history of India and Persia in the 5th and 6th centuries, and was known to the Byzantine writers, who call them 'E40aXiroL, Ei)Owytroi, NecbOaAtroc or 'A(3b€Xoi.
Also the "unit" e l (or e,) considered as a number of the system is merely a shortened form for the complex number (+I) ei +0e2+ +oen.