'other' is not a member of 'Object'?

Hi Guys, so I have this script I tried from this tutorial: - YouTube

and I copied the exact same thing, yet I am getting an error i am not sure of means as I am still a beginner.

#pragma strict

var damage = 10;

function OnCollisionEnter (collisionInfo) 
{
	//when there is a collision, it will send a message and look for the ApplyDamage function
	collisionInfo.other.SendMessage("ApplyDamage", damage, SendMessageOptions.DontRequireReceiver);
}	//when bullet hits, its going to tell the healthbar to decrease life

I have applied the script onto my bullet and everything but unity keeps telling me that ‘other’ is not a member of ‘object’…I cant figure out whats wrong as the script is the exact same as the one in the tutorial. Any help would be appreciate!

You need to type your parameter. Line 5 should be:

 function OnCollisionEnter (collisionInfo : Collision)