Forms mean shapes in general, an outline of any three dimensional object in the space. Forms can be created by combining two or more shapes and can be accentuated with the help of other elements like texture, patterns and colors. A well-defined form establishes harmony and additional forms add balance to the space. There are two types of forms – Geometric (man-made) and Natural (organic). Also forms are categorized as open and closed; open forms are those that can be looked into and closed forms are those that are enclosed by a closed surface. A solid understanding of the above mentioned elements i.e. space and line is required to achieve a good form.
Design cheat sheet
Form and shape are similar to line in that they it can define the level of formality and overall theme of the space.
Think about the shapes made by unintentionally defining them through the outer edges of other objects – negative space.
Open forms can be a seating area or elevator surround. A reception area can be an opportunity to utilize a form that can be reinforced elsewhere or be a standalone showpiece
Shape is what you see when you look at a schematic, or look at an interior scene from one angle. It is 2D
Form is 3D, that is, the shapes as you experience them as you move around them. It is a challenge to think about how forms interact with one another, and with a person, as they enter and experience the space from different angles and views.