1. A difficult problem or task that requires sophisticated thinking, multiple approaches, or specialized knowledge to solve
Climate change represents a complex challenge for governments worldwide.
Mudanças climáticas representam um desafio complexo para governos em todo o mundo.
2. A multifaceted problem involving interconnected variables or competing interests
Implementing new technology while maintaining legacy systems is a complex challenge.
Implementar nova tecnologia mantendo sistemas legados é um desafio complexo.