word-forming element meaning "bulk, mass," used from 19c., especially in medical use, "tumor," from Latinized form of Greek ogkos (pronounced "onkos") "bulk, size, mass, weight, swelling," in Modern Greek "tumor," a word of uncertain origin.
word-forming element meaning "a speaking, discourse, treatise, doctrine, theory, science," from Greek -logia (often via French -logie or Medieval Latin -logia), from -log-, combining form of legein "to speak, tell;" thus, "the character or deportment of one who speaks or treats of (a certain subject);" from PIE root *leg- (1) "to collect, gather," with derivatives meaning "to speak (to 'pick out words')." Often via Medieval Latin -logia, French -logie. In philology "love of learning; love of words or discourse," apology, doxology, analogy, trilogy, etc., Greek logos "word, speech, statement, discourse" is directly concerned.
Others are reading
Definitions of oncology from WordNet
the branch of medicine concerned with the study and treatment of tumors;