形容詞 dangerous:

1. involving or causing danger or risk; liable to hurt or harm
   同義詞：unsafe
2. causing fear or anxiety by threatening great harm
   同義詞：grave, grievous, serious, severe, life-threatening

1. This decision creates a dangerous precedent.
   這個(gè)決定開創(chuàng)了一個(gè)危險(xiǎn)的先例。
2. Icy roads are dangerous.
   覆蓋著冰的道路很危險(xiǎn)。
3. That dog is a dangerous brute; it bites people.
   那條狗是危險(xiǎn)的畜牲，它咬人。
4. A little learning is a dangerous thing.
   一知半解，為害不淺。
5. We should pay more attention to the infection of young people with dangerous ideologies.
   我們應(yīng)該多注意危險(xiǎn)的思想意識(shí)對(duì)年輕人的影響。
6. Many dangerous diseases are carried by insects.
   許多危險(xiǎn)的疾病是由昆蟲傳播的。
7. It's dangerous to be so near to the tiger.
   離老虎那么近是很危險(xiǎn)的。
8. His dog looks dangerous.
   他的狗看上去很危險(xiǎn)。

dan.ger.ous

adj.（形容詞）
Involving or filled with danger; perilous.
危險(xiǎn)的：涉及到或充滿危險(xiǎn)的；危機(jī)四伏的
Being able or likely to do harm.
能或可能受危害的

【引伸】
dan.gerously
adv.（副詞）
dan.gerousness
n.（名詞）