English

The Rosetta Stone.

Proper noun

Rosetta Stone

1. A large inscribed stone found near Rosetta, Egypt, in 1799; later used as a basis for understanding many previously undecipherable examples of hieroglyphic writing.
2. (hence) Any source of information crucial to interpreting.

   My friend’s carefully-compiled notebook was the Rosetta Stone that opened understanding of the physics lectures.

Translations