Kappa
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 Kappa facts

• In the system of Greek numerals, Kʹ has a value of 20
• It was derived from the Phoenician letter kaph
• Letters that arose from kappa include the Roman K and Cyrillic К
• Greek proper names and placenames containing kappa are often written in English with "c" due to the Romans' transliterations into the Latin alphabet: Constantinople, Corinth, Crete
• All formal modern romanizations of Greek now use the letter "k", however: Thessaloniki, Kalamata, Nikaia
• The cursive form ϰ is generally a simple font variant of lower-case kappa, but it is encoded separately in Unicode for occasions where it is used as a separate symbol in math and science
• In mathematics, the kappa curve is named after this letter; the tangents of this curve were first calculated by Isaac Barrow in the 17th century