Proportion: Proportion refers to how one part of an object relates to whole object in size, such as the size of an arm in relation to the rest of the body.
Informal: It is similar to scale.
Source:https://www.reference.com/art-literature/proportion-art-da87fb5057fc8fd2
rule of thirds: The rule of thirds states that if you divide any composition into thirds, vertically and horizontally, then place the key elements of your image either along these lines or at the junctions of them, you’ll achieve a more pleasing arrangement and more interesting and dynamic compositions.
Informal: Guides to help center the focus of a composition.
Source:http://www.creativebloq.com/art/how-use-rule-thirds-art-21619159
Golden Rule:
Closely related to the Fibonacci Sequence (which you may remember from either your school mathematics lessons or Dan Brown’s novel The Da Vinci Code), the Golden Ratio describes the perfectly symmetrical relationship between two proportions.
Approximately equal to a 1:1.61 ratio, the Golden Ratio can be illustrated using a Golden Rectangle: a large rectangle consisting of a square (with sides equal in length to the shortest length of the rectangle) and a smaller rectangle.
Golden Ratio
If you remove this square from the rectangle, you’ll be left with another, smaller Golden Rectangle. This could continue infinitely, like Fibonacci numbers – which work in reverse. (Adding a square equal to the length of the longest side of the rectangle gets you increasingly closer to a Golden Rectangle and the Golden Ratio.)
Golden Ratio 2
Informal: Geometric compositions leading to infinite repetition in shape.
