(1) only用作副词时，意思是“仅仅，只不过”；but作为副词，用作only解时是书面语。
- She is only/but a child.
她不过是个孩子。 - He had intended to stay but a brief period in Dublin.
他本打算在都柏林只待上短暂的一段时间。 - We can but try.
我们只能试试。 - Deeds are fruits, words are but leaves. 〈谚〉
行动是果实，言辞只不过是叶子。
(2) mere为形容词，意思是“仅仅，单单”，“只要，只是”，用作定语。
- But an army is a mere means to an end.
但是一支军队仅仅是实现目的的手段。 - At the mere thought of Mary his heart began to beat fiercely.
只要一想到玛丽，他的心就开始剧烈地跳动。 - It was mere waste of breath to argue with a person in so unreasonable a state of mind.
跟一个如此不通情理的人争论只是白费力气。 - I don't understand why he gives himself such airs; he is a mere nobody.
我不明白他为什么摆这样的架子，他只是一个无名小辈。 - The mere sight of a dog makes him afraid.
只要一看见狗他就害怕。 - A mere two miles isn't too far to walk.
只有两英里，并非远得不能走着去。
(3) merely是副词，意思是“仅仅，只不过，只是”。
- Their explanations were merely poor excuses.
他们的解释只不过是些蹩脚的借口。 - I believed that she was merely teasing him.
我认为她只不过是与他逗乐。 - Marx did not merely see the surface, but penetrated beneath.
马克思并不是仅仅看到表面，而是深入到事物内部。
