1. the living together in close association of two dissimilar organisms especially when mutually beneficial
2. a cooperative relationship

Francisco José de Goya y Lucientes was a Spanish romantic painter and printmaker. He is considered the most important Spanish artist of the late 18th and early 19th centuries and throughout his long career was a commentator and chronicler of his era. Immensely successful in his lifetime, Goya is often referred to as both the last of the Old Masters and the first of the moderns. He was also one of the great portraitists of his time.

Goya was born to a lower-middle-class family in 1746, in Fuendetodos in Aragon. He studied painting from age 14 under José Luzán y Martinez and moved to Madrid to study with Anton Raphael Mengs. He married Josefa Bayeu in 1773; their life was characterised by an almost constant series of pregnancies and miscarriages, and only one child, a son, survived into adulthood. Goya became a court painter to the Spanish Crown in 1786 and this early portion of his career is marked by portraits of the Spanish aristocracy and royalty, and Rococo style tapestry cartoons designed for the royal palace.

He was guarded, and although letters and writings survive, little is known about his thoughts.

Severus Alexander was Roman Emperor from 222 to 235 and the last emperor of the Severan dynasty. He succeeded his cousin Elagabalus upon the latter's assassination in 222. His own assassination marked the epoch event for the Crisis of the Third Century—nearly 50 years of civil wars, foreign invasion, and collapse of the monetary economy.

Alexander was the heir to his cousin, the 18-year-old Emperor who had been murdered along with his mother Julia Soaemias, by his own guards, who, as a mark of contempt, had their remains cast into the Tiber river. He and his cousin were both grandsons of the influential and powerful Julia Maesa, who had arranged for Elagabalus' acclamation as emperor by the famous Third Gallic Legion. It was the rumor of Alexander's death that triggered the assassination of Elagabalus and his mother. His 13-year reign was the longest reign of a sole emperor since Antoninus Pius. He was also the second-youngest ever sole legal Roman Emperor during the existence of the united empire, the youngest being Gordian III.

As emperor, Alexander's peacetime reign was prosperous.

The Eastern Front of World War II was a theatre of conflict between the European Axis powers and co-belligerent Finland against the Soviet Union, Poland and other Allies, which encompassed Central Europe, Eastern Europe, Northeast Europe, and Southeast Europe from 22 June 1941 to 9 May 1945. It is known as the Great Patriotic War in the Soviet Union and its successor states, while in Germany it was called the Eastern Front.

The battles on the Eastern Front of the Second World War constituted the largest military confrontation in history. They were characterised by unprecedented ferocity, wholesale destruction, mass deportations, and immense loss of life due to combat, starvation, exposure, disease, and massacres. Of the estimated 70–85 million deaths attributed to World War II, around 30 million occurred on the Eastern Front. The Eastern Front was decisive in determining the outcome in the European theatre of operations in World War II, eventually serving as the main reason for the defeat of Nazi Germany and the Axis nations.

The two principal belligerent powers were Germany and the Soviet Union, along with their respective allies.