A tempera, or temper, is a medium used to bind a range of pigments. Tempers include egg yolk (tempera), gum arabic, oil and egg white. Temper(a) in historical artistic terms is not confined to egg yolk. Egg tempera has become the modern byword for medieval painting, but in fact egg tempera was mostly popular in Southern Europe, northern Europe favouring oil and animal glue based paints. Tempera (or egg tempera) is the primary type of artist's paint and associated art techniques that were prevalent in Southern Europe's Middle Ages, and the required medium for Orthodox icons. It is paint made by binding pigment in an egg medium. However, the term tempera in modern times is also used by some manufacturers to refer to ordinary poster paint, which is a form of gouache that has nothing to do with real egg tempera.