Final answer:
The Rosetta Stone contains three different languages: Hieroglyphic, Demotic, and Greek, which were key in deciphering the ancient Egyptian hieroglyphs.
Step-by-step explanation:
To answer the question about how many different languages are there on the Rosetta Stone, there are three. The celebrated Rosetta Stone features the same text inscribed in three different scripts: Hieroglyphic, Demotic, and Greek. This artifact has been pivotal in deciphering Egyptian hieroglyphs, offering insights into this ancient form of writing. Scholars and linguists were able to understand hieroglyphs by comparing them with the Greek, which was already known, paving the way for enormous advances in our understanding of ancient Egyptian language and culture.