Error in my runtime. Namespace error

So this bit of code i'am having problems with. I'm trying to make a turn based strategy game and trying to implement a grid like board for my players to play on. the only error i'm getting out of this is 'IHasNeightbours'1' can't be found. are you missing a using directive or assembly reference. The line it points me too is line "public class Tile: GridObject, IHasNeighbours". I'm fairly new at this and taking some tutorials... so sorry if it seems like a dumb question.

 using System.Collections.Generic;
 using System;
 using System.Linq;
 using UnityEngine;
 
 public class Tile: GridObject, IHasNeighbours
 {
    public static List NeighbourShift
     {
         get
         {
             return new List<Point>
                 {
                     new Point(0, 1),
                     new Point(1, 0),
                     new Point(1, -1),
                     new Point(0, -1),
                     new Point(-1, 0),
                     new Point(-1, 1),
                 };
         }
     }
 
     public void FindNeighbours(Dictionary<Point, Tile> Board,
         Vector2 BoardSize, bool EqualLineLengths)
     {
         List<Tile> neighbours = new List<Tile>();
 
         foreach (Point point in NeighbourShift)
         {
             int neighbourX = X + point.X;
             int neighbourY = Y + point.Y;
             //x coordinate offset specific to straight axis coordinates
             int xOffset = neighbourY / 2;
 
             //If every second hexagon row has less hexagons than the first one, just skip the last one when we come to it
             if (neighbourY % 2 != 0 && !EqualLineLengths &&
                 neighbourX + xOffset == BoardSize.x - 1)
                 continue;
             //Check to determine if currently processed coordinate is still inside the board limits
             if (neighbourX >= 0 - xOffset &&
                 neighbourX < (int)BoardSize.x - xOffset &&
                 neighbourY >= 0 && neighbourY < (int)BoardSize.y)
                 neighbours.Add(Board[new Point(neighbourX, neighbourY)]);
         }
 
         AllNeighbours = neighbours;
         }
 &#9;}