STRATUM

PRONUNCIATION: (STRAY-tuhm, STRAT-uhm)
plural strata (STRAY-tuh, STRAT-uh) or stratums

MEANING: noun: A layer of something, as rock, tissue, people at an economic level, etc.

ETYMOLOGY: From Latin stratum (cover), past participle of sternere (to spread). Ultimately from the Indo-European root ster- (to spread), which also gave us structure, industry, destroy, street, Russian perestroika, stratagem, and stratocracy. Earliest documented use: 1599. Nowadays, the word is often seen in its plural form used as a singular, similar to agenda, errata, etc.
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STRADUM - one single priceless old violin

ASTRA-TUM - the pocket antacid tablet preferred by the ISS crew

SPRATUM - why Jack could eat no fat, and his wife no lean