Scripting Error Help Needed

I'm a newbie and making a game where you are a ball and you roll around and stuff but when I scripted the jumping it stopped working and gave the errors, expecting ), found '='. Also ';' expected. Insert a semicolon at the end. But I'm not aware of where I have missed a semi colon. Could anyone help me please? Here's the code it is not very long

 var rotationspeed = 100;
 var jumpheight = 8;
 
 private var isFalling = false;
 
 function Update () 
 {
     //Handle ball rotation.
     var rotation : float = Input.GetAxis ("Horizontal") * rotationspeed;
     rotation *= Time.deltaTime;
     rigidbody.AddRelativeTorque (Vector3.back * rotation);
 
     if (Input.GetKeyDown(KeyCode.W) && isFalling == false);
     (
         rigidbody.velocity.y = jumpheight;
     )
     isFalling = true;
 }
 
 function OnCollisionStay ()
 {
     isFalling = false;
 }