word-forming element, especially in scientific compounds, meaning "life, life and," or "biology, biology and," or "biological, of or pertaining to living organisms or their constituents," from Greek bios "one's life, course or way of living, lifetime" (as opposed to zoe "animal life, organic life"), from PIE root *gwei- "to live." The correct usage is that in biography, but since c. 1800 in modern science it has been extended to mean "organic life," as zoo-, the better choice, is restricted in modern use to animal, as opposed to plant, life. Both are from the same PIE root. Compare biology.
1610s, "deductive reasoning," from Latin synthesis "collection, set, suit of clothes, composition (of a medication)," from Greek synthesis "composition, a putting together," from syntithenai "put together, combine," from syn- "together" (see syn-) + tithenai "to put, to place," from reduplicated form of PIE root *dhe- "to set, put." From 1733 as "a combination of parts into a whole." Earlier borrowed in Middle English as sintecis (mid-15c.). Plural syntheses.
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Definitions of biosynthesis from WordNet
production of a chemical compound by a living organism;