This is the 563rd most frequent Indonesian word.
ilegal
Illegal.
Here, 'ilegal' is used as an adjective describing a prohibited activity, to give legal context.
Menebang pohon di hutan lindung adalah kegiatan ilegal.
Cutting down trees in a protected forest is an illegal activity.
The word 'ilegal' is used as an adverb ('secara ilegal') here to describe the manner of an action being unlawful, focusing on the way the activity is conducted.
Perdagangan hewan langka secara ilegal merugikan ekosistem.
Trafficking endangered animals illegally harms the ecosystem.
In this example, 'ilegal' is used to characterize objects that are against the law, providing a description of their nature.