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from Greek, literally e psilon "bare -e-, -e- and nothing else," in contradistinction to the diphthong -ai-, which has the same sound. Greek psilon "smooth, simple" is of uncertain origin.
epsilon ep·si·lon (ěp'sə-lŏn', -lən)
Symbol ε The fifth letter of the Greek alphabet.
The fifth in a series.
Of or relating to the fifth member of a particular ordered set.
Relating to or characterizing a polypeptide chain that is one of five types of heavy chains present in immunoglobins.
(symbol e), fundamental physical constant expressing the naturally occurring unit of electric charge, equal to 1.6021892 1019 coulomb, or 4.80325 1010 electrostatic unit (esu, or statcoulomb). In addition to the electron, all freely existing charged subatomic particles thus far discovered have an electric charge equal to this value or some whole-number multiple of it. Quarks, which are always bound within larger subatomic particles such as protons and neutrons, have charges of 13 or 23 of this value