Final answer:
The 2015 encyclical by Pope Francis is called 'Laudato si'' in both English and Latin, and it addresses environmental issues and sustainable development.
Step-by-step explanation:
The English name for Pope Francis' encyclical issued in 2015 is Laudato si', and the Latin name is Laudato si', mi' Signore, which translates to "Praise be to you, my Lord." This encyclical focuses on the environment and sustainable development, calling for action against human-caused climate change. It holds the distinction of being one of the most influential papal documents released in recent times, addressing not only Catholics but all people around the world. An encyclical is typically written in Latin, the traditional language of the Roman Catholic Church, before being translated into other languages for wider dissemination.