The Middle Ages
The expression 'the Middle Ages' - always with the definite article and in the plural, and with initial capitals for 'Middle' and 'Ages' - is used in two different ways. More commonly, the expression refers to the period of European history which extends from the end of the fifth century CE to the middle of the fifteenth century CE (i.e., c500 CE-c1450 CE). The expression is also sometimes used, though nowadays not very often, to refer exclusively to the latter half of this period, i.e., the period from the beginning of the eleventh to the middle of the fifteenth century (c1000 CE-c1450 CE).
The Middle Ages are so called because they are the period which comes between Classical Antiquity (when the civilisations of Greece and Rome flourished) and the Modern Era, these being the three periods into which most historians, from the seventeenth century onwards, have divided European history.
It is neither necessary nor possible to set precise dates for the beginning and end of the Middle Ages; and in the light of their particular interests different historians have quite properly taken them to begin and end at different points. However, the Middle Ages are often said to begin in 476 CE with the deposition of the Roman emperor Romulus Augustulus, the last ruler of the Western Roman Empire, and to end in 1453 with the capture of Constantinople by the Ottoman Turks and the fall of the Byzantine Empire - though those historians who see the Middle Ages as ending with the Renaissance would prefer an earlier date.
Historians distinguish different periods within the Middle Ages. Thus the period from the end of the fifth century to 1000 CE is usually referred to as 'the Early Middle Ages' (or sometimes as the Dark Ages); the period from 1000 CE to 1300 CE as 'the High Middle Ages'; and the period after 1300 CE as 'the Late Middle Ages'.
The adjective which means 'of or relating to the Middle Ages' is 'medieval' (the spelling preferred in American English) - alternatively spelt 'mediaeval' or 'mediæval' (see æ (spelling)), and pronounced with the stress on the third syllable me-di-EE-verl, IPA: /,mɛ dɪ 'iː vəl/. The word comes from the Latin medium (middle) and aevum (age). The adjective 'medieval' is also sometimes used in informal speech to mean not 'of or relating to the Middle Ages' but 'very old-fashioned or primitive' - as in 'Their washing machine is positively medieval' or 'His attitude to women is medieval'.
Be careful not to confuse 'the Middle Ages' and 'middle age' (always in the singular with lower case initial letters and never with an article) - middle age is the period of life which comes between youth and old age. The adjective from 'middle age' is 'middle-aged'. In the case of human beings middle age used to be taken to be the period of life between the ages of 40 and 60, but in the UK today many men and women in their 40s would strongly object to being described as 'middle-aged'.
Although in English the Middle Ages are always referred to in the plural, the equivalent expression in some other European languages is in the singular - in German das Mittelalter, in French le Moyen Age, in Italian il medio evo, and in Spanish la Edad Media.
See further The Dark Ages.