Noun

1. A stone that can be stepped on in crossing something, especially a marsh or creek
2. Something used as a way to progress to something or somewhere else.

   "He was full of ambition, and force, and life, intending all sorts of great things, and meaning to make his position a stepping stone to all that was excellent in public life."

Adjective

1. To be as a stepping stone, a good place to begin or cross over to.

   Esperanto can make a good stepping stone language to Latin, which may be difficult for amateur linguists.