A blackboard or a chalkboard is a reusable writing surface on which text or drawings are made with sticks of calcium sulphate or calcium carbonate, known, when used for this purpose, as chalk. Blackboards were originally made of smooth, thin sheets of black or dark grey slate stone.
NASA scientist Homer E. Newell Jr. explaining principles of altitude, pressure, and temperature, c. 1973
A chalkboard with an eraser in the chalk tray
Stick-slip effect with a chalk on a blackboard
Middle school chemistry on a blackboard in Beijing, China, 2011
Writing is the act of creating a persistent representation of human language. A writing system uses a set of symbols and rules to encode aspects of spoken language, such as its lexicon and syntax. However, written language may take on characteristics distinct from those of any spoken language.
The Rosetta Stone, with writing using three different scripts, was instrumental in deciphering Egyptian hieroglyphs
Olin Levi Warner, tympanum representing Writing, above exterior of main entrance doors, Thomas Jefferson Building, Washington DC, 1896
Documents that are connected by hyperlinks
Globular envelope with a cluster of accountancy tokens, Uruk period, from Susa – Louvre Museum
