#Common chinese synonyms discriminated#-4-奥秘、机密、秘密 While 奥妙can only used as a none, both 机密 and 秘密 can be used either as adjectives or as nouns. All three terms share the idea of something that one doese not know. 奥妙 connotes mystery and wonder and it usually refers to some natural phenomena which are still beyond one's comprehension, or to other abstract things that may make people mystified: Different from 奥妙，which is objectively unknown to everyone, 机密 and 秘密 both refer to something that one deliberately hides from being known by others. 机密, as a more formal term than 秘密, usually means something important and secret. It therefore often applies to some important information of a state, a party, a military unit, or an enterprise. 秘密, on the other hand, is a more generic term, referring to anything that is not to be made public or to be shared by others, whether it is of a personal matter or of the business of a state or an organization. Hence it has a wider application than 机密： In terms of usage, 秘密 can serve as an adverbial modifying a verb in a sentence, whereas 机密 cannot. Besides, one also needs to notice the following common word collocations. *我们一定要探索宇宙更多的奥秘。 *这是国家机密，我不能告诉任何人。 *秘密武器，秘密投票，秘密访问，秘密会谈 Exercise 1.姑娘的（ ）和烦恼只有他知道； 2.只要不涉及国家（）和安全，新闻记者可以自由采访； 3.人类还要等多久才能了解生命的（）呢？