pentagon [L16th] The ancient Greeks’ expertise in geometry means that many geometrical forms have Greek names. The five-sided pentagon is formed from penta ‘five’ and gonia ‘angle’, just as polygon [M16th] is formed from the word for ‘many’ plus -gon and diagonal [M16th] with dia ‘through’. Penta is also found in words such as the mystic figures of the pentangle [LME], pentacle [M16th], and pentagram [E19th], and in the pentathlon [E17th] ‘five contest’, once the original events of leaping, running, discus-throwing, spear-throwing, and wrestling of ancient Greek and Roman games. Fifty is found in Pentecost [OE] which came via ecclesiastical Latin from Greek pentēkostē (hēmera) ‘fiftieth (day)’. The Jewish festival of Shavuoth is held on the fiftieth day after the second day of Passover. The Christian festival is held on the seventh Sunday after Easter commemorating the descent of the Holy Spirit on the disciples as recorded in Acts 2.