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avocet

(Encyclopedia)avocet ăvˈəsĕt [key], common name for a long-legged wading bird about 15 to 18 in. (37.5–45 cm) long, related to the snipe and belonging to the same family as the stilt. The American avocet or b...

rudder

(Encyclopedia)rudder, mechanism for steering an airplane or a ship. In ships it is a flat-surfaced structure hinged to the stern and controlled by a helm. When the ship is on a straight course, the rudder is in lin...

thresher shark

(Encyclopedia)thresher shark, long-tailed, warm-water shark, genus Alopias. The upper fork of its tail is slender and sickle-shaped and is about equal in length to the rest of the body. This shark uses its tail str...

darter, bird

(Encyclopedia)darter or anhinga ănhĭngˈgə [key], common name for a very slender, black water bird very closely related to the cormorant. It frequents the wooded borders of freshwater lakes, rivers, and swamps i...

parcel post

(Encyclopedia)parcel post, sending of packages through the mail service. At the congress of the Universal Postal Union in Paris in 1878, an international parcel-post system was established. The British parcel-post ...

annual rings

(Encyclopedia)annual rings, the growth layers of wood that are produced each year in the stems and roots of trees and shrubs. In climates with well-marked alternations of seasons (either cold and warm or wet and dr...

Tagus

(Encyclopedia)Tagus tāˈgəs [key], Span. Tajo, Port. Tejo, river, c.585 mi (940 km) long, rising in the mountains E of Madrid, E Spain, and draining the central part of the Iberian Peninsula. The Tagus flows nort...

sodium hydroxide

(Encyclopedia)sodium hydroxide, chemical compound, NaOH, a white crystalline substance that readily absorbs carbon dioxide and moisture from the air. It is very soluble in water, alcohol, and glycerin. It is a caus...

sodium silicate

(Encyclopedia)sodium silicate, any one of several compounds containing sodium oxide, Na2O, and silica, Si2O, or a mixture of sodium silicates. Sodium orthosilicate is Na4SiO4 (or 2Na2O·SiO2); sodium metasilicate i...

speedometer

(Encyclopedia)speedometer, instrument that indicates speed. A cable from an automotive speedometer is attached to the rear of the transmission of an automobile; the cable turns at a rate proportional to the speed o...