In music, a fugue () is a type of contrapuntal composition or technique of composition for a fixed number of parts, normally referred to as "voices", irrespective of whether the work is vocal or instrumental."fugue" The Concise Oxford Dictionary of Music. Ed. Michael Kennedy. Oxford University Press, 1996. In the Middle Ages, the term was widely used to denote any works in canonic style; by the Renaissance, it had come to denote specifically imitative works. "Fugue fugue; Ger. Fuge; Lat., It., Sp., fuga." The Harvard Dictionary of Music, (New England, 2003), Since the 17th Century see for discussion of the changing use of the term throughout Western music history. the term fugue has described what is commonly regarded as the most fully developed procedure of imitative counterpoint. A fugue opens with one main theme, the subject, which then sounds successively in each voice in imitation; when each voice has entered, the exposition is complete; usually this is followed by a connect
Source:
http://en.wikipedia.org/wiki/Fugue