Form is the three-dimensional shape and modelling of buildings and the spaces they define. Buildings and spaces can take many forms, depending upon their: size and shape in plan; height; bulk – their volume; massing – how bulk is shaped into a form; building lines – the alignment of building frontages along a street; and relationship to the plot boundary – and whether they share party walls or not. In the case of spaces, their form is influenced by the buildings around them.