(For the meaning in physical science see Dynamics (physics).)
In music, dynamics are degrees of loudness.
Dynamics range from pp (pianissimo) meaning "very quiet" to ff (fortissimo) meaning "very loud." It is uncommon but not unheard of to see louder or softer dynamics (such as ppp or fffff), especially in Romantic works. All dynamics are relative in nature; there is not a defined decibel level for a certain marking.