Help! I don't know how to fix this. Errors CS1041, CS1525, CS8025

I have been stumped and I don't know how to fix the following problems with the code - CS1041: Identifier expected - CS1525: Unexpected symbol (', expecting )', ,', ;', [', or ='

I am trying to get a bullet to disappear after colliding with something and can't seem to get it.

I am very new to Unity and coding in general and would be greatly appreciated if someone can help me see my errors. Thanks

 using UnityEngine;
 using System.Collections;
 
 public class Despawn : MonoBehaviour {
     
 
     
     
     
 function OnCollisionEnter(other : Collision){
     var despawnTime = 1;
     
     yield WaitForSeconds(despawnTime);
     Destroy(bullet);
 }
     
     
     // Use this for initialization
     void Start () {
     
     }
     
     // Update is called once per frame
     void Update () {
     }    
 }