Copper ( /ˈkɒpər/ KOP-ər) is a chemical element with the symbol Cu (from Latin: cuprum) and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; a freshly exposed surface has a reddish-orange color. It is used as a conductor of heat and electricity, a building material, and a constituent of various metal alloys.

The metal and its alloys have been used for thousands of years. In the Roman era, copper was principally mined on Cyprus, hence the origin of the name of the metal as сyprium (metal of Cyprus), later shortened to сuprum. Its compounds are commonly encountered as copper(II) salts, which often impart blue or green colors to minerals such as turquoise and have been widely used historically as pigments. Architectural structures built with copper corrode to give green verdigris (or patina). Decorative art prominently features copper, both by itself and as part of pigments.

Copper(II) ions are water-soluble, where they function at low concentration as bacteriostatic substances, fungicides, and wood preservatives. In sufficient amounts, they are poisonous to higher organisms; at lower concentrations it is an essential trace nutrient to all higher plant and animal life. The main areas where copper is found in animals are liver, muscle and bone.

A boy is a young male human, usually child or adolescent. When he becomes an adult he's described as a man. The most apparent thing that differentiates a boy from a girl is that a boy typically has a penis while girls do not. However some intersex children with ambiguous genitals, and biologically female transgender children, may also be classified or self-identify as a "boy".

The term "boy" is primarily used to indicate biological sex distinctions, cultural gender role distinctions or both. The latter most commonly applies to adult men, either considered in some way immature or inferior, in a position associated with aspects of boyhood, or even without such boyish connotation as age-indiscriminate synonym. The term can be joined with a variety of other words to form these gender-related labels as compound words.

The word "boy" comes from Middle English boi, boye ("boy, servant"), related to other Germanic words for boy, namely East Frisian boi ("boy, young man") and West Frisian boai ("boy"). Though the exact etymology is obscure, the English and Frisian forms probably derive from an earlier Anglo-Frisian *bō-ja ("little brother"), a diminutive of the Germanic root *bō- ("brother, male relation"), from Proto-Indo-European *bhā-, *bhāt- ("father, brother"). The root is also found in Flemish boe ("brother"), Norwegian dialectal boa ("brother"), and, through a reduplicated variant *bō-bō-, in Old Norse bófi, Dutch boef "(criminal) knave, rogue", German Bube ("knave, rogue, boy"). Furthermore, the word may be related to Bōia, an Anglo-Saxon personal name.

Twit may refer to: