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dolphin, aquatic mammal

(Encyclopedia)dolphin, aquatic mammal, any of the small toothed whales of the family Delphinidae, numbering more than 50 species. These include the true, or beaked, dolphins, the killer whale, the pilot whale, and ...

water pollution

(Encyclopedia)water pollution, contamination of water resources by harmful wastes; see also sewerage, water supply, pollution, and environmentalism. The United States has enacted extensive federal legislation to ...

Mollusca

(Encyclopedia)Mollusca məlŭsˈkə [key], taxonomic name for the one of the largest phyla of invertebrate animals (Arthropoda is the largest) comprising more than 50,000 living mollusk species and about 35,000 fos...

Persian Gulf

(Encyclopedia)Persian Gulf, arm of the Arabian Sea, 90,000 sq mi (233,100 sq km), between the Arabian peninsula and Iran, extending c.600 mi (970 km) from the Shatt al Arab delta to the Strait of Hormuz, which link...

Carboniferous period

(Encyclopedia)Carboniferous period kärbənĭfˈərəs [key], fifth period of the Paleozoic era of geologic time (see Geologic Timescale, tablegeologic timescale, table), from 350 to 290 million years ago. The pl...

Antarctica

(Encyclopedia)CE5 Antarctica ăntärkˈtĭkə, –ärˈtĭkə [key], the fifth largest continent, c.5,500,000 sq mi (14,245,000 sq km), asymmetrically centered on the South Pole and almost entirely within the An...

Malay Peninsula

(Encyclopedia)Malay Peninsula məlāˈ, māˈlā [key], southern extremity (c.70,000 sq mi/181,300 sq km) of the continent of Asia, lying between the Andaman Sea of the Indian Ocean and the Strait of Malacca on the...

Chechnya

(Encyclopedia)Chechnya chəchĕnˈ [key], republic (1990 est. pop. 1,300,000, with neighboring Ingushetia), c.6,100 sq mi (15,800 sq km), SE European Russia, in the N Caucasus. Grozny is the capital. Prior to 1992 ...

potassium

(Encyclopedia)potassium pətăsˈēəm [key], a metallic chemical element; symbol K [Lat. kalium=alkali]; at. no. 19; at. wt. 39.0983; m.p. 63.25℃; b.p. 760℃; sp. gr. .862 at 20℃; valence +1. Potassium is a s...

Ohio, river, United States

(Encyclopedia)Ohio, river, 981 mi (1,579 km) long, formed by the confluence of the Allegheny and Monongahela rivers in SW Pa., at Pittsburgh; it flows northwest, then generally southwest to enter the Mississippi Ri...