From the A Word A Day mailing list:

ylem (I-lum) noun

A form of matter hypothesized by proponents of the big bang theory to have existed before the formation of the chemical elements.

(Middle English, universal matter, from Old French ilem, from Medieval Latin hylem, accusative of hyle, matter, from Greek hule.)

"Alpher and Gamow focused on the point when the universe had cooled to a state consisting of radiation and matter, ylem, Greek for the primordial stuff of life."

Joseph D'Agnese, "The last Big Bang man left standing", Discover, Jul. 1999.

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