安定 vs 稳定.
安定 can be an adjective, a verb or a noun.
1. 安定 as an adjective: stable, settled. 安定 (adj.) is the opposite of "disturbed" and it's about order of a society, so we often see it being used with society, social stability, political environment, etc.
Interesting fact: because 安定 is related to social environment, you see 安定 being used in place names a lot, esp. in Beijing, for instance: 安定门 （Andingmen，a gate in Beijing's Ming-era city wall)
2. 安定 as a verb: to stabilize, to calm, to reassure, to settle down. This is used on one's nerves, the public or people's minds, social order, etc.
3. 安定 as a noun: (Med.) valium, diazepam.
稳定 can be an adjective or a verb.
1. 稳定 as an adjective: stable, firm, steady.
This can be used in the same way as 安定 to describe social order. They are interchangeable, for instance:
安定的社会秩序 = 稳定的社会秩序
In the following, we usually only use 稳定, not 安定:
- when describing something at a more personal level (one's medical situation, job or family life), e.g. 稳定的工作 [nphr] stable job
- when describing something quantitative, e.g. price, income, increase, decrease, stock market. e.g. 最近，北京的物价比较稳定。[phr] Recently the commodity prices in Beijing is relatively stable.
All in all, 稳定 emphasizes on not changing or fluctuating very much.
2. 稳定 as a verb: to stabilize, to steady. 稳定 (verb) is interchangeable with 安定 (verb):
安定社会秩序 = 稳定社会秩序
安定情绪 = 稳定情绪