1. A task, pursuit, or undertaking that requires significant effort, skill, or concentration to accomplish
Learning a new language is a difficult activity that requires dedication.
Aprender um novo idioma é uma atividade difícil que requer dedicação.
2. An exercise or assignment that presents challenges or obstacles to completion
The final exam included several difficult activities to test the students' knowledge.
O exame final incluiu várias atividades difíceis para testar o conhecimento dos alunos.