How would I be able to subtract from a variable when it hits something? (OnCollisionEnter)

I have been learning Javascript and I was wondering if I could subtract a variable if the game object came in contact with a certain object. For example, if an enemy touched the character, it would say GAME OVER. Something along those lines.

Yes, its quite simple.

a) Make sure the the character, and the collided object both have colliders attached.

b) Make sure that at-least one of them is a (non-kinematic) rigid-body, generally the character.

Remember that “OnCollisionEnter” will not work with the built-in “CharacterController” that comes with Unity. For that you will need to use “OnControllerColliderHit” instead.

#pragma strict

var Health:int =10;

function OnCollisionEnter(collision : Collision) 

if(collision.gameObject.tag == "Monster")
	Health = Health-1;
	Debug.Log("Health reduced to " + Health);
if(Health <= 0)
	Debug.Log("Character died");