word-forming element; -cracy with a connective -o-.

word-forming element, before vowels oct-, from combining form of Latin octo "eight," from PIE root *octo(u)- "eight" (see eight). Words made from Greek elements or derived from Greek typically are octa-.

word-forming element abstracted from alcoholic (q.v.); also see -aholic, which has tended to replace it in word formation.

word-forming element meaning "like, like that of, thing like a ______," from Latinized form of Greek -oeidēs (three syllables), from eidos "form," related to idein "to see," eidenai "to know;" literally "to see" (from PIE *weid-es-, from root *weid- "to see"). The -o- is connective or a stem vowel from the previous element. Often implying an incomplete or imperfect resemblance to the thing indicated.

word-forming element making adjectives from nouns in -oid; see -oid + -al (1).

word-forming element in chemistry, variously representing alcohol, phenol, or in some cases Latin oleum "oil" (see oil (n.)).

commercial suffix, probably originally in pianola (q.v.).

word-forming element indicating "branch of knowledge, science," now the usual form of -logy. Originally used c. 1800 in nonce formations (commonsensology, etc.), it gained legitimacy by influence of the proper formation in geology, mythology, etc., where the -o- is a stem vowel in the previous element.

The second element is prop[erly] -logy ( -logue, etc.), the -o- belonging to the preceding element; but the accent makes the apparent element in E[nglish] to be -ology, which is hence often used as an independent word. [Century Dictionary] 

word-forming element; see -ology + -ist.

word-forming element, from Greek -oma, with -o-, lengthened stem vowel + -ma, suffix forming neuter nouns and nouns that indicate result of verbal action (equivalent of Latin -men); especially taken in medical use as "morbid growth, tumor," based on sarcoma, carcinoma.