This is the 411th most frequent Japanese word.
危険
Danger.
Here, the word '危険' is used as a noun to identify a state of danger associated with the bridge.
この橋は危険なので、渡らないでください。
This bridge is dangerous, so please do not cross it.
In this sentence, '危険' is part of the compound term '危険性,' which refers to the level or nature of danger.
火山活動が危険性を高めています。
Volcanic activity is increasing the level of danger.
In this example, '危険' is used as part of the na-adjective '危険な' to describe a dangerous situation.