This is the 4752nd most frequent Catalan word.
residual
Residual: remaining or leftover.
In this case, 'residual' characterizes 'risc' (risk), implying the part of risk that remains after mitigation efforts.
Hem d'eliminar el risc residual quan planifiquem futures mesures.
We must eliminate the residual risk when planning future measures.
In this sentence, 'residual' is used as an adjective describing 'aigua' (water), indicating that it is leftover or waste water.
L'aigua residual ha estat tractada abans de ser abatuda al riu.
The wastewater has been treated before being released into the river.
Here, 'residual' describes 'soroll' (noise), referring to background or remaining noise that persists.