why is this script not working???

So i have made my code and i keep getting the error
Assets/loAD.js(3,5): BCE0005: Unknown identifier: ‘SceneManager’.
while using this code
function OnTriggerEnter() {
And if it is so bad can you please rewrite i need it so when a object collides with another it will load a new scene.

My first guess would be that you are missing

uses UnityEngine.SceneManagement;

from your directives at the top of the file. But this is only a guess as you ave not provided much to go on. If this is not the problem could you please post the whole script to help us understand what is going on?