Final answer:
Ars nova is the term used for the transformative musical style of the fourteenth century, characterized by complex polyphony and advanced rhythmic notation.
Step-by-step explanation:
Ars nova, which translates to "new art," categorically refers to the innovative musical style that evolved during the fourteenth century. This period saw the transition from the modal rhythms and monophonic melodies of the earlier medieval period to more complex polyphonic textures and the development of new rhythmic patterns. The term itself was popularized by the theorist and composer Philippe de Vitry, known for his contributions to the new rhythmic notation system.
Ars nova is associated with a refinement of rhythmic notation, which allowed composers to write music with greater rhythmic independence in the various voices and opened the way for more intricate and expressive compositions. Rather than just for describing a modest development in music style, 'ars nova' signifies a dramatic shift that had broad implications for the development of Western music, laying the groundwork for subsequent musical periods.
The final answer to the question is: D) expressive new musical style of the fourteenth century. In a two line explanation: Ars nova refers to the revolutionary style of music in the fourteenth century featuring complex polyphony and new rhythmic patterns, not architectural, artistic, or literary movements. It led to significant advancements in musical notation and composition.