What dynamic marking indicates the instruction to play "loud"?

The dynamic marking that indicates the instruction to play "loud" is forte, which is typically represented by the letter "f." In musical notation, forte signifies a strong sound and requires the performer to produce a powerful and resonant tone. This marking is foundational in music, establishing a clear level of intensity that differentiates it from more subdued dynamics.

Fortepiano refers to a sudden change from loud to soft; it indicates a loud note that is immediately followed by a softer one. Fortissimo, another terminology, means "very loud" and is a step beyond forte. It signifies an even greater intensity than forte does. Espressivo, on the other hand, conveys an expressive or emotive performance but does not specifically denote a volume level. Thus, forte is the most direct instruction for playing loudly.