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.