consciousness 是形容词 conscious 的派生名词；awareness是形容词 aware 的派生名词。（所有两者的区别与其形容词的区别相似）

 consciousness 表示“意识”有两层意思：

一是指人是否处于清醒状态或是否有知觉，此时只能用 consciousness，不能用 awareness。如：

She experienced a brief loss of consciousness. = She lost consciousness [=became unconscious] briefly. 她暂时失去了知觉。

 He slowly regained consciousness [=became conscious again; woke up] after the surgery. 手术后他慢慢恢复了知觉。

I can't remember any more—I must have lost consciousness. 我再也记不起什么了——我当时一定是失去了意识。

She could faintly hear voices as she began to regain consciousness (=wake up). 当她开始恢复知觉时，隐约听到有人在说话的声音。

He lost consciousness after his accident and never recovered/regained it. 事故发生后他便失去了知觉，再也没有苏醒过来。

consciousness 表示“意识”的另一个用法是表示政治、生活等方面的“观念”“看法”等，此时与 awareness 同义，常可互换。如：

Environmental awareness has increased over the years. 这些年来人们的环境意识增强了。（牛津）

This will increase public consciousness of the pollution issue. 这将提高公众对污染问题的意识。（朗文）