a·phaer·e·sis or a·pher·e·sis (ə-fěr'ĭ-sĭs) n.
pl.a·phaer·e·ses or a·pher·e·ses (-sēz') The loss of one or more sounds from the beginning of a word, as in till for until.
[Late Latin, from Greek aphairesis, from aphairein, to take away : apo-, apo- + hairein, to take.] aph'ae·ret'ic (āf'ə-rět'ĭk) adj.
aph·e·re·sis (āf'ə-rē'sĭs) Medicine A procedure in which blood is drawn from a donor and separated into its components, some of which are retained, such as plasma or platelets, and the remainder returned by transfusion to the donor. Also called hemapheresis.