Keyword that means "nothing"?

In my game I want it that when I advance to the next level, my camera comes with me(is not destroyed), but when I die in my game I want that when I go back to the main menu my camera is destroyed. I am wondering if there is a word or phrase that means "nothing".

My script:

if(Application.LoadLevel ("mainmenu"))
{
    //what would i put here?    
}
else
{
    function Awake () 
    {
        DontDestroyOnLoad (this);
    }   
}

this script is attached to my level 1 main camera. if there is no word/or phrase i can put in to replace the //what would I put here? comment, then what can i do?

To answer your question literally, the ";" is the empty statement, so in theory you could put that in there. But instead of this:

if(condition)
{
    ;
}
else
{
    // do something
}

you can simply reverse the condition:

if(!condition)
{
    // do something
}

However, what you actually want to do doesn't work the way you describe. For starters, "function Awake()" cannot be within the if/else. Keeping objects between levels alive while making sure there is only one copy when returning to the level that created your object is tricky and laden with pitfalls, especially since Unity doesn't behave correctly or consistently in this regard.

But what you describe, creating your camera in "level 1", and keeping it alive until you return to "mainmenu", should be possible by attaching something like this to your Camer a in level 1:

function Awake(){
    DontDestroyOnLoad();
}

function OnEnable(){
    if(Application.loadedLevelName=="mainmenu")
        Destroy(gameObject);
}

However, when doing this you also have to take care that there are no other "Main Cameras" in your other levels, so either remove them (which makes testing these levels difficult), disable them by hand before you make a build (which is tedious), or by script (which is complicated and prone to the same pitfalls as above).

EDIT: Why do you need to keep the camera between levels? if all you want to keep is the orientation and position of the camera, it is much better to create a script that does just that, instead of trying to keep the whole Camera persistent between levels.