Dynamics
Dynamics indicate the loudness of the music, and can be combined with other instructions to give the performer a detailed understanding of how to perform the music, while also leaving room for interpretation.
Dynamics can indicate an immediate change in volume or a gradual change over a specified duration. By default, they are placed below the staff for instruments and above the staff for voices.
You can add qualifying and expressive text to dynamics that can give stylistic direction context alongside the volume level, for example, espressivo indicates that a passage is played loudly but also with expressive feeling.
While almost all expression text is written in italics, dynamics such as and use a bold italic font.