Risky, Unsafe, Dangerous, Danger, Peril, Hazard
noun, な adjective
Something that is dangerous and risky is probably pretty risky, dangerous, and unsafe.
きけん
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
これは世界一危険な仕事です。
This is the most dangerous job in the world.
駅ではよく、「危険ですから黄色い線の内がわまでお下がりください」というアナウンスが流れています。
In stations, there is often an announcement that says, "It will be unsafe, so please stay behind the yellow line."
コタツに入ると、気持ち良すぎて出られなくなるので危険です。
Getting in a kotatsu is dangerous because it just feels too good and you can no longer get out.