1. subjects or matters that are difficult to understand, involving many interconnected parts or factors
The professor explained complex topics in a way that students could understand.
O professor explicou tópicos complexos de uma forma que os alunos pudessem entender.
2. multifaceted issues requiring deep analysis and careful consideration
Climate change and economics are complex topics that require expertise.
Mudanças climáticas e economia são tópicos complexos que requerem expertise.