Style. An art movement is a tendency or style in art with a specific common philosophy or goal, followed by a group of artists during a restricted period of time, or, at least, with the heyday of the movement defined within a number of years. Art movements were especially important in modern art, when each consecutive movement was considered as a new avant-garde. According to theories associated with modernism and the concept of postmodernism, art movements are especially important during the period of time corresponding to modern art. The period of time called modern art is posited to have changed approximately halfway through the 20th century and art made afterward is generally called contemporary art. Postmodernism in visual art begins and functions as a parallel to late modernism and refers to that period after the modern period called contemporary art. The postmodern period began during late modernism, and according to some theorists postmodernism ended in the 21st century. During the period of time corresponding to modern art each consecutive movement was often considered a new avant-garde. Also during the period of time referred to as modern art each movement was seen corresponding to a somewhat grandiose rethinking of all that came before it, concerning the visual arts. Generally there was a commonality of visual style linking the works and artists included in an art movement. Verbal expression and explanation of movements has come from the artists themselves, sometimes in the form of an art manifesto, and sometimes from art critics and others who may explain their understanding of the meaning of the new art then being produced. In the visual arts, many artists, theorists, art critics, art collectors, art dealers and others mindful of the unbroken continuation of modernism and the continuation of modern art even into the contemporary era, ascribe to and welcome new philosophies of art as they appear. Postmodernist theorists posit that the idea of art movements are no longer as applicable, or no longer as discernible, as the notion of art movements had been before the postmodern era. There are many theorists however who doubt as to whether or not such an era was actually a fact; or just a passing fad. The term refers to tendencies in visual art, novel ideas and architecture, and sometimes literature. In music it is more common to speak about genres and styles instead. See also cultural movement, a term with a broader connotation. As the names of many art movements use the-ism suffix, they are sometimes referred to as isms.