The 1958 ''Encyclopédie Fasquelle'' defines a period as follows:
"A complex Phrase , in which the various parts are enchained."
Another definition:
"In traditional music...a group of Measure s comprising a natural division of the Melody ; usually regarded as comprising two or more contrasting or complementary phrases and ending with a Cadence ." (''Harvard Dictionary of Music'', 1969)
SOURCE
Nattiez, Jean-Jacques (1990). ''Music and Discourse: Toward a Semiology of Music'' (''Musicologie générale et sémiologue'', 1987). Translated by Carolyn Abbate (1990). ISBN 0691027145.
