In general terms, line establishes shape and form. It suggests movement and leads or moves the eye around the room. Lines are either straight or curved. Vertical lines suggest formality and dignity. Horizontal lines are more restful, relaxed and casual.
Diagonal lines create a sense of drama.
Curved lines add interest and relief. They reflect the personality and ambience of a room and are considered to be softer and therefore more feminine. In any one room, the various forms should be harmonious and composed of similar types of lines. One of the most important tenets of interior decoration is that comfort and function should not be sacrificed in order to use a certain form. For example, if a chair is pleasing to look at but uncomfortable to sit in, it is not functional, and is not good interior design.