In the physical sense, breadth is defined as the measure of the second-largest dimension of an object or its width, whereas depth is generally the distance from the top to bottom or from the front to back of an object. Breadth and depth are also used to explain how a person understands the world. People can have breadth or depth knowledge about particular subjects, notes the University of Guelph.
Breadth also refers to the size or the extent of something. In abstract terms, someone with a lot of breadth is liberal and has a wide-ranging worldview. In art, breadth refers to the overall mood of a piece as opposed to its fine details, according to Dictionary.com.
Depth has meanings beyond physicality as well. Someone who has depth displays hidden qualities that are not readily known. Depth can refer to a vast amount of knowledge or a serious situation. Macmillan Dictionary states that in art, a piece has depth when there is an illusion of distance from the foreground to the background or if it has bright colors.
Academically, breadth refers to the ability to connect many disciplines of study in a coherent manner. Depth is when someone masters one particular body of knowledge. Both breadth and depth are needed to achieve independence of thought, according to the University of Guelph.