21 : Idioms & Phrases
atomic number 21
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noun a white trivalent metallic element; sometimes classified in the rare earth group; occurs in the Scandinavian mineral thortveitite
scandium; Sc.
WordNet
june 21
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noun June 21, when the sun is at its northernmost point
midsummer; summer solstice.
WordNet
trisomy 21
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noun a congenital disorder caused by having an extra 21st chromosome; results in a flat face and short stature and mental retardation
mongolism; Down syndrome; mongolianism; Down's syndrome.