Axis is the most basic and most common organizing principle. Simply stated, axis is an imaginary line that is used to organize a group of elements in a design. In diagrams, axis is represented as a dashed line.
Axis is mainly used to align elements. When elements are arranged around an axis, the design feels ordered. As with most things in life, we enjoy things that are ordered because they feel more stable, comfortable and approachable.
When we encounter something linear, such as an axis, we naturally follow the line in a direction. If we arrive on a street, we walk down the street. If we open an elevator into a long hallway, we walk down the hallway. Lines prompt movement and interactions. The direction of movement depends on the end points. A defined end point signals a place to start or stop.
Although axis is an imaginary line, you can make it more apparent if the edges of surrounding elements are well defined. A common example of this concept in architecture is a city street. The city street is an axis that is reinforced by the buildings on both sides. If a portion of the street is missing a building on one or both sides, the street’s axis would not feel as strong.
If an end point is undefined, you will follow the axis until you reach something of interest or are tired of interacting with the axis. While the concept of an undefined end point in architecture is uncommon since it’s difficult for something architectural to go on forever, it’s becoming more popular in product design with infinite scrolls.
Symmetry is when elements are arranged in the same way on both sides of an axis. Perfect symmetry is when elements are mirrored over the axis and exactly the same on both sides.
Symmetry adds balance to a design. When elements are the same on both sides of an axis, the design feels harmonious. If we design a street with five houses on one side and five on the other, walking down the street would feel comfortable because the arrangement of homes is balanced.
Designs are asymmetrical if the arrangement of elements are different on both sides of an axis. If we design a street with five houses on one side and one on the other, the street will feel unbalanced and perhaps uncomfortable.
Hierarchy is when an element appears more important in comparison to other elements in a design.
An element will appear more hierarchical if it is larger than other elements in a design. We naturally look first at the largest element in a design. If there are five windows on the front of a building, and one is twice the size of the others, our attention will focus on the biggest window first.
An element can also appear more hierarchical if it is different than other elements in a design. We naturally look first at the irregular shape in a design. If there are five of the same windows and one door on the front of a building, our attention will focus on the door first.
Last but not least, we can place elements in more hierarchical positions. Within a circle, the center is the most hierarchical. The end of an axis is naturally more hierarchical than points along the line.
Rhythm is the movement created by a repeated pattern of forms.
The best way to understand rhythm is to think of a song. Songs have rhythm when a piece of the song repeats. When listening to a song with good rhythm, we recognize the pattern and begin to expect beats.
A break in rhythm will appear more hierarchical. Think about a song. When a song has a repeated rhythm and the rhythm is broken, something quite special usually happens.