A design may mean something, may represent something. It may relate to a specific topic. For example a church or a mosque.
Rhythm, like in music, means repetition or continuation in a pattern or of a unit. This is a very common feature in Architecture.
Contrast is used to either provide focus on a specific part of the design or to show a major difference between two sections of the design.
Closely associated with Meaning, symbolism is used to directly symbolize something through a design. For example, Most churches have a plan shaped like a cross, symbolizing Christianity.
Scale is a very important aspect of a good design. For instance, if doors or windows are not to scale with an average human in mind, they would seem incorrect and the design would be bad.
Form means shape or structure. Form is like a medium. Adding or subtracting from a form gives us a design.
Once again, closely associated with meaning, Imagery is more straight forward than symbolism. This church was designed in the memory of the brave men and women of the U.S. Air Force who lost their lives in the line of action.
Pattern and rhythm are not to be confused. Pattern must be repetition only. It may not be a sequence or progression. A pattern may be in rhythm, but rhythm may not be a pattern.
One of the most important principles, proportion helps a design make sense technically. Imagine what would happen if stairs were too high or too broad. Stairs must follow a standard proportion in order to be convenient.