Contrast

From Andy Rutledge's article on Contrast and Meaning:

Design is largely an exercise in creating or suggesting contrasts, which are used to define hierarchy, manipulate certain widely understood relationships, and exploit context to enhance or redefine those relationships …all in an effort to convey meaning. Contrast is important because the meaningful essence of any thing is defined by its value, properties, or quality relative to something else. That’s right: nothing has much meaning by itself, which is one reason why design is important.

The function of contrast in defining meaning can be explained by comparing fundamental opposites: dark/light, soft/hard, fast/slow. Examples like these are useful because everyone understands the extremes they imply, but while there are extremes, there are no absolutes. The values are merely relative.

For instance, a cheetah is generally considered to be fast. But a cheetah is quite slow compared to a jet airplane. So saying “a cheetah is fast” is only meaningful when some relevant context is also communicated or assumed. Likewise, stating that “element X in the page layout is important” is only meaningful when the relative importance of that and all other elements has been established. In other words, every element on the page you’re designing has to be positioned, styled, sized, or otherwise distinguished in accordance with its specific importance and place in the overall communicative objective. If you neglect even one component, it may work to subvert your entire effort.

In addition to defining meaning and relationships, contrast is closely tied to human perception and survival instincts, as we’ll examine later, and this makes contrast a powerful and essential tool for designers. Simply put, contrast is at the root of almost everything you’ll accomplish with design.

There are several primary forms of contrast that designers typically use, including the following: (though there are many more)