This is a day never to be forgotten. 

This is a rule never to be broken. 

请问这里的never to be done作定语是什么用法？

可不可以说this is a day never forgotten. 这是一个没有被忘记的日子。

【答】在a day never to be forgotten 和a rule never to be broken 两个词组中，简单地说就是不定式作定语。只是不定式有点特殊：1. 被动式；2. 不定式前加了否定副词never（比not 的否定程度更强烈）。

▲ never to do sth.（被动式：never to be done）可以作如下句子成分：

1. 作定语：

He made a resolution never to repeat the act.  他决心不再采取那种行动。

He was conscious of a border never to be crossed. 他意识到有一条永远不能逾越的鸿沟。

2. 作主语：

Never to play computer games again is his promise.不再玩电脑游戏是他的承诺。

It was his destiny never to see her again. 命运注定他再也见不着她。

3. 作宾语：

I promise never to reveal his secret. 我答应决不泄漏他的秘密。

He makes it a rule never to borrow money. 他无论如何也不向别人借钱。

4. 作状语：

He went off to the war never to return alive. 他去参加战争，没能活着回来。

One day Mr. Nelson disappeared from town, never to be seen again.  有一天芮先生在城里不见了，以后再没有人看到他。

5. 作宾补：

I told him never to set foot in my house again. 我告诉他再也别踏进我家的门。

My parents taught me never to tell lies. 我父母告诫我千万不要说谎。

6. 作表语：

His promise is never to play computer games again. 他承诺不再玩电脑游戏。

His guiding principle is never to stop learning.  他的指导原则是永不停顿地学习。

▲一般而言，不定式表示的动作往往指未来发生的事件。所以，作定语时可以转换成一个将来时态的定语从句。例如：

This is a day never to be forgotten. = This is a day which will never be forgotten.

This is a rule never to be broken. = This is a rule which will never be broken. 

以上两句的will never 除了表将来，还带有一种意愿。

关于“可不可以说This is a day never forgotten. 这是一个没有被忘记的日子。”我认为，不可这样表达。应改为：

This is a day which has never been forgotten. 这是一个不曾忘记的日子。