A dimension is the measurement of something in physical space. You might give the painters every dimension of the rooms you want painted, including depth, height, and width.
In addition to physical objects, dimension can describe something less tangible, such as the magnitude or extent of something. You might be shocked by the dimension of damage from the explosion down the street. Dimension can also be a feature of something, such as an experience, situation, flavor, or thing. Painting your bedroom purple will add a mystical dimension to your dwelling, especially if you add unicorn accents.