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paper

(Encyclopedia)paper, thin, flat sheet or tissue made usually from plant fiber but also from rags and other fibrous materials. It is used principally for printing and writing on but has many other applications. The ...

zinc oxide

(Encyclopedia)zinc oxide, chemical compound, ZnO, that is nearly insoluble in water but soluble in acids or alkalies. It occurs as white hexagonal crystals or a white powder commonly known as zinc white. Zinc white...

rosewood

(Encyclopedia)rosewood, popular name for the ornamental wood of several species of tropical trees, especially for the heartwood of certain leguminous trees of the genus Dalbergia of the family Leguminosae (pulse fa...

quince

(Encyclopedia)quince, shrub or small tree of the Asian genera Chaenomeles and Cydonia of the family Rosaceae (rose family). The common quince (Cydonia oblonga) is a spineless tree with edible fruits cultivated from...

Empedocles

(Encyclopedia)Empedocles ĕmpĕdˈəklēz [key], c.495–c.435 b.c., Greek philosopher, b. Acragas (present Agrigento), Sicily. Leader of the democratic faction in his native city, he was offered the crown, which h...

ipecac

(Encyclopedia)ipecac ĭpˈĭkăk [key], drug obtained from the dried roots of a creeping shrub, Cephaelis (or Psychotria) ipecacuanha, native to Brazil but cultivated in other tropical climates. There are three var...

abrasive

(Encyclopedia)abrasive, material used to grind, smooth, cut, or polish another substance. Natural abrasives include sand, pumice, corundum, and ground quartz. Carborundum (silicon carbide) and alumina (aluminum oxi...

sunstone

(Encyclopedia)sunstone. 1 Crystal mineral thought by some to have been used by the Vikings as an aid to navigation, especially in conditions of low visibility due to clouds or fog when the position of the sun was u...

Diogenes of Apollonia

(Encyclopedia)Diogenes of Apollonia ăpəlōˈnēə [key], 5th cent. b.c., Greek philosopher. An eclectic, he reverted to the Milesian tradition of a century earlier in seeking to explain the constitution of all ma...

mother-of-pearl

(Encyclopedia)mother-of-pearl or nacre nāˈkər [key], the iridescent substance that forms the lining of the shells of some fresh-water and some salt-water mollusks. Like the pearl it is a secretion of the mantle,...