Need help with simple script

I’m watching a video on how to make a simple unity game, but I have been stuck for about an hour and would appreciate some help.

Error I am getting: Assets/BallControl.js(21,18): BCE0044: expecting (, found ‘OnCollisionStay’.`

#pragma strict

var RotationSpeed = 100;
var JumpHeight = 8;

private var IsFalling = false;

function Update (){
	//Hand Ball Rotation
	var Rotation : float = Input.GetAxis ("Horizontal") * RotationSpeed;
	Rotation *= Time.deltaTime;
	GetComponent.<Rigidbody>().AddRelativeTorque (Vector3.back * Rotation);

	if (Input.GetKeyDown (KeyCode.W)) and (IsFalling == false){
		GetComponent.<Rigidbody>().velocity.y = JumpHeight;

	IsFalling = true;

	//Check To See If Instance Is On Ground
	function OnCollisionStay();
		IsFalling = false;

I don’t use JavaScript and I’m on my phone but the parse error seems to be caused the oncollisionenter function being declared within the update function. You will need to close the update function with a curly bracket and then declare oncollisionenter. Oncollisionenter doesn’t need to be called by the update function either because it will be called whenever a collision occurs.