Why do I keep getting this error?

I keep getting this error and I can't find the problem I don't know if I worded something wrong or I am missing a typo, but I can't get it to go away no matter what I do

Assets/chcarcterClasses/BaseCharacter.cs(101,64): error CS0246: The type or namespace name `ModifyingAttribute' could not be found. Are you missing a using directive or an assembly reference?

using UnityEngine; using System.Collections; using System; //acces the enum class

public class BaseCharacter : MonoBehaviour {

 private string _name;
 private int _level;
 private uint _freeEx;
 
 private Attribute[]_primaryAttribute;
 private vital[]_vital;
 private skill[]_skill;
   
 public void Awake(){
 
 _name = string.Empty;
     _level =0;
     _freeEx =0;
     
     _primaryAttribute = new Attribute[Enum.GetValues(typeof(AttributeName)).Length];
 
     _vital = new vital[Enum.GetValues(typeof(VitalName)).Length];
     
     _skill = new skill[Enum.GetValues(typeof(SkillName)).Length];
     
     SetUpPrimaryAttribute();
     SetUpVital();
     SetUpSkills();
     
 }
 
 
 // Use this for initialization
 void Start () {
 
 }
 
 // Update is called once per frame
 void Update () {
 
 }
 
 public string Name {
     get{ return _name;}
     set{ _name = value; }
 }
 
 public int Level {
     get{ return _level;}
     set{ _level= value;}
 }
 
 public uint FreeEx{
     get{ return _freeEx;}
     set{ _freeEx = value;}
         
     }
     
 public void AddEx(uint ex){
         _freeEx += ex;
             CalculateLevel();
     }
 
 //take advantage  of the players skills and assign them to a level
     public void CalculateLevel(){
     
     }
     
 private void SetUpPrimaryAttribute(){
     for(int cnt = 0; cnt < _primaryAttribute.Length; cnt++){
         _primaryAttribute[cnt] = new Attribute();
 }
             }
 
 private void SetUpVital(){
         for( int cnt = 0; cnt <_skill.Length; cnt++){
                 _vital[cnt]= new vital();
             }
             
 }
 
 private void SetUpSkills(){
             for(int cnt = 0; cnt < _skill.Length; cnt++){
                 _skill[cnt] = new skill();
             }
 }
 
 public Attribute GetPrimaryAttribute(int index){
     return _primaryAttribute[index];
 }
 public vital GetVital(int index){
     return _vital[index];
 }
 public skill GetSkill(int index){
     return _skill[index];
 }
 
 private void SetUpVitalModifiers(){
     //Health
     GetVital((int)VitalName.Healh).AddModifier(new ModifyingAttribute()(GetPrimaryAttribute((int)AttributeName.Constitution), .5f));
     //energy
     GetVital((int)VitalName.Energy).AddModifier(new ModifyingAttribute()(GetPrimaryAttribute((int)AttributeName.Constitution), 1));
     
     // mana
     GetVital((int)VitalName.Mana).AddModifier(new ModifyingAttribute()(GetPrimaryAttribute((int)AttributeName.Willpower),1));
     
     
 }
 private void SetUpSkillModifiers()
 {
 //melee offence
         GetSkill((int)SkillName.Magic_Offence).AddModifier(new ModifyingAttribute(GetPrimaryAttribute((int)AttributeName.Might),.33f));
         GetSkill((int)SkillName.Magic_Offence).AddModifier(new ModifyingAttribute(GetPrimaryAttribute((int)AttributeName.NImbelness),.33f));
 //melee defence
         GetSkill((int)SkillName.Melee_Defence).AddModifier(new ModifyingAttribute(GetPrimaryAttribute((int)AttributeName.Speed),.33f));
         GetSkill((int)SkillName.Magic_Defence).AddModifier(new ModifyingAttribute(GetPrimaryAttribute((int)AttributeName.Constitution),.33f));
 //magic offence
         GetSkill((int)SkillName.Magic_Offence).AddModifier(new ModifyingAttribute(GetPrimaryAttribute((int)AttributeName.Constitution),.33f));
         GetSkill((int)SkillName.Magic_Offence).AddModifier(new ModifyingAttribute(GetPrimaryAttribute((int)AttributeName.Willpower),.33f));
 //magic defence
         GetSkill((int)SkillName.Magic_Defence).AddModifier(new ModifyingAttribute(GetPrimaryAttribute((int)AttributeName.Concentration),.33f));
         GetSkill((int)SkillName.Magic_Defence).AddModifier(new ModifyingAttribute(GetPrimaryAttribute((int)AttributeName.Concentration),.33f));
 //ranged offence
         GetSkill((int)SkillName.Ranged_Offence).AddModifier(new ModifyingAttribute(GetPrimaryAttribute((int)AttributeName.Concentration),.33f));
         GetSkill((int)SkillName.Ranged_Offence).AddModifier(new ModifyingAttribute(GetPrimaryAttribute((int)AttributeName.Speed),.33f));
 //ranged defence
         GetSkill((int)SkillName.Ranged_Defence).AddModifier(new ModifyingAttribute(GetPrimaryAttribute((int)AttributeName.Speed),.33f));
         
         }
 public void StatUpdate(){
 for(int cnt =0; cnt <_vital.Length; cnt++)
         _vital[cnt].Update();
     for(int cnt = 0; cnt < _skill.Length; cnt++)
         _skill[cnt].Update();
 }

}