word-forming element meaning "earth, the Earth," ultimately from Greek geo-, combining form of Attic and Ionic gē "the earth, land, a land or country" (see Gaia).
before vowels gloss-, word-forming element meaning "tongue," from Greek glosso-, used as a combining form of glōssa (Attic glōtta) "tongue" (see gloss (n.2)). Also sometimes meaning "gloss, word inserted as explanation," as in glossography "the writing of glosses."
before vowels ornith-, word-forming element meaning "bird, birds," from combining form of Greek ornis (genitive ornithos; plural ornithēs) "a bird," in Attic generally "domestic fowl, cock or hen," which often was added to the specific name of the type of bird, from PIE *or- "large bird" (see erne).
For "bird" Greek also had ptēnon (plural peteina), related to pteron "wing," from the root meaning "to fly."
often before vowels pseud-, word-forming element meaning "false; feigned; erroneous; in appearance only; resembling," from Greek pseudo-, combining form of pseudēs "false, lying; falsely; deceived," or pseudos "falsehood, untruth, a lie," both from pseudein "to tell a lie; be wrong, break (an oath)," also, in Attic, "to deceive, cheat, be false," but often regardless of intention, a word of uncertain origin. Words in Slavic and Armenian have been compared; by some scholars the Greek word is connected with *psu- "wind" (= "nonsense, idle talk"); Beekes suggests Pre-Greek origin.
Productive in compound formation in ancient Greek (such as pseudodidaskalos "false teacher," pseudokyon "a sham cynic," pseudologia "a false speech," pseudoparthenos "pretended virgin"), it began to be used with native words in later Middle English with a sense of "false, hypocritical" (pseudoclerk "deceitful clerk;" pseudocrist "false apostle;" pseudoprest "heretical priest;" pseudoprophete; pseudofrere) and has been productive since then; the list of words in it in the OED print edition runs to 13 pages. In science, indicating something deceptive in appearance or function.