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oxygen

(Encyclopedia)oxygen, gaseous chemical element; symbol O; at. no. 8; interval in which at. wt. ranges 15.99903–15.99977; m.p. −218.4℃; b.p. −182.962℃; density 1.429 grams per liter at STP; valence −2. T...

fur trade

(Encyclopedia)fur trade, in American history. Trade in animal skins and pelts had gone on since antiquity, but reached its height in the wilderness of North America from the 17th to the early 19th cent. The demand ...

sulfur

(Encyclopedia)CE5 Sulfur crystals sulfur or sulphur sŭlˈfər [key], nonmetallic chemical element; symbol S; at. no. 16; interval in which at. wt. ranges 32.059–32.076; m.p. 112.8℃ (rhombic), 119.0℃ (mon...

Maya, indigenous people of Mexico and Central America

(Encyclopedia)Maya mīˈə, Span. mäˈyä [key], indigenous people of S Mexico and Central America, occupying an area comprising the Yucatán peninsula and much of the present state of Chiapas in Mexico, Guatemala...

reproductive system

(Encyclopedia)CE5 Reproductive system reproductive system, in animals, the anatomical organs concerned with production of offspring. In humans and other mammals the female reproductive system produces the femal...

exploration

(Encyclopedia)exploration, travel to a part of the earth that is relatively unknown to the traveler's culture, historically often motivated by a desire for colonization, conquest, or trade. See also space explorati...

infertility

(Encyclopedia)infertility, inability to conceive or carry a child to delivery. The term is usually limited to situations where the couple has had intercourse regularly for one year without using birth control. The ...

enzyme

(Encyclopedia)enzyme, biological catalyst. The term enzyme comes from zymosis, the Greek word for fermentation, a process accomplished by yeast cells and long known to the brewing industry, which occupied the atten...

tuberculosis

(Encyclopedia)tuberculosis (TB), contagious, wasting disease caused by any of several mycobacteria. The most common form of the disease is tuberculosis of the lungs (pulmonary consumption, or phthisis), but the int...

flag, symbolic cloth

(Encyclopedia)flag, piece of cloth, usually bunting or similar light material, plain, colored, or bearing a device, varying in size and shape, but often oblong or square, used as an ensign, standard, or signal or f...