There are many similar words in Chinese language in both appearance and meaning. 肯定and确定is one of the most frequently seen groups. The former one can function as both verb and adjective. When it is used as an adjective, it carries the meaning of being positive or affirmative like 他的语气很肯定and他的回答是肯定的. Students who learn Mandarin Chinese should know the verb 肯定means to admit the existence and authenticity of things like肯定他们的做法. It can be used to express sure about something. For example, 去北京的事，我现在还不敢肯定.
However, the word 确定is a verb applied to mean to ascertain something, carrying the tone of making something settled like 确定开会的时间和地点. To tell them apart, you need to be clear that 肯定is to accept something while 确定is to fix something from the unstable state, carrying the meaning of “remain unchanged”.
It is essential for those who just begin to learn to speak Chinese to know the similarities and differences of the group of words 空气and气氛. The most common meaning of 空气is air like 新鲜空气. But it can be applied to indicate certain spirit or tendency in certain environment. We can say 制造紧张空气.
You may often hear Chinese people say 热烈的氛围. The word 氛围indicates the spiritual expression or scene that gives people strong feeling in certain environment. You can say 有好的氛围. However, one point that the foreign students who learn Chinese online free should know is 空气has a larger application range. Except for the meaning of the spiritual expression and tendency that氛围carries, 空气can be used to describe the air. For example, 唐古拉山口海拔5000米，这里空气十分稀薄.
Of course, the beginners of Chinese language teaching can explain and understand 空气and气氛with the help of respectively air and atmosphere, making it more clear to see the differences.