1. The fundamental or primary reasons or factors that are the root source of something, often hidden beneath surface symptoms or effects
The doctor investigated the underlying causes of the patient's illness.
O médico investigou as causas subjacentes da doença do paciente.
2. The deep-seated or basic elements that explain why something happened, rather than obvious explanations
Understanding the underlying causes of poverty is essential for policy makers.
Compreender as causas subjacentes da pobreza é essencial para os formuladores de políticas.