Mensuralism refers to the theory and practice of musical notation in the Middle Ages and Renaissance periods. Synonyms for this term include "mensuration," "metrical notation," and "mensural notation." All of these terms describe the way that music was written down using symbols and markings to indicate rhythm, pitch, and other musical elements. Another related term is "proportional notation," which refers to a system of notation that used fractions to indicate rhythmic proportions. These terms are important in studying the history of music and understanding how different styles of music developed over time.