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Cubango

(Encyclopedia)Cubango ōkəvängˈgō [key], river, c.1,000 mi (1,610 km) long, rising in the highlands of central Angola, W central Africa, and flowing southeast, across the Caprivi Strip, Namibia, to the Okavango...

amenorrhea

(Encyclopedia)amenorrhea āmĕnˌərēˈa, əmĕnˌ– [key], cessation of menstruation. Primary amenorrhea is a delay in or a failure to start menstruation; secondary amenorrhea is an unexpected stop to the menstr...

Baroja y Nessi, Pío

(Encyclopedia)Baroja y Nessi, Pío pēˈō bärōˈhä ē nāsˈsē [key], 1879–1956, Spanish novelist from the Basque Country, member of the group of writers known as the Generation of '98. He left medicine to d...

retrovirus

(Encyclopedia)retrovirus, type of RNA virus that, unlike other RNA viruses, reproduces by transcribing itself into DNA. An enzyme called reverse transcriptase allows a retrovirus's RNA to act as the template for th...

notochord

(Encyclopedia)notochord nōˈtəkôrdˌ [key], in biology, supporting rod running most of the length of animals of the phylum Chordata and present at varying times in the life cycle. Composed of large cells packed ...

Persephone

(Encyclopedia)Persephone prōsûrˈpənē [key], in Greek and Roman religion and mythology, goddess of fertility and queen of the underworld. She was the daughter of Zeus and Demeter. When she was still a beautiful...

Boussingault, Jean Baptiste Joseph Dieudonné

(Encyclopedia)Boussingault, Jean Baptiste Joseph Dieudonné zhäN bätēstˈ zhôzĕfˈ dyödônāˈ bo͞osăNgōˈ [key], 1802–87, French agricultural chemist. He was professor of chemistry at Lyons and later pr...

tapeworm

(Encyclopedia)tapeworm, name for the parasitic flatworms forming the class Cestoda. All tapeworms spend the adult phase of their lives as parasites in the gut of a vertebrate animal (called the primary host). Most ...

sun, in astronomy

(Encyclopedia)CE5 Structure of the sun sun, intensely hot, self-luminous body of gases at the center of the solar system. Its gravitational attraction maintains the planets, comets, and other bodies of the sola...

sleep

(Encyclopedia)sleep, resting state in which an individual becomes relatively quiescent and relatively unaware of the environment. During sleep, which is in part a period of rest and relaxation, most physiological f...