The Middle Ages lasted from the 5th century into the 15th century. In European history it is the period from the fall of the Roman Empire until the Renaissance.
The Medieval period is sometimes divided into the Early Middle Ages; the High Middle ages, which lasted from about the 10th until the 14th century; and the Late Middle Ages.
Most people became Christian in the Early Middle Ages and the church gained authority. Feudalism was established as the social and political structure in Europe, and the Gothic architecture developed particularly in the 12th century.
The transition from the Middle Ages to the modern period began when European society changed, due to economic expansion, political centralization, and the loss of influence of the church.
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Bibliography:
"Middle Ages." The Columbia Encyclopedia, 6th ed.. 2013. Encyclopedia.com. Web. 10 Jan. 2014. <http://www.encyclopedia.com>.
"Middle Ages." World Encyclopedia. 2005. Encyclopedia.com. Web. 10 Jan. 2014. <http://www.encyclopedia.com/doc/1O142-MiddleAges.html>.