A pattern, from the French patron, is a theme of reoccurring events or objects, sometimes referre to as elements of a set. These elements repeat in a predictable manner. It can be a template or model which can be used to generate things or parts of a thing, especially if the things that are created have enough in common for the underlying pattern to be inferred, in which case the things are said to exhibit the unique pattern. Pattern matching is the act of checking for the presence of the constituents of a pattern, whereas the detecting for underlying patterns is referred to as pattern recognition. The question of how a pattern emerges is accomplished through the work of the scientific field of pattern formation. Patterns are also related to repeated shapes or objects, sometimes referred to as elements of the series. Some patterns (for example, many visual patterns) may be directly observable, such as simple decorative patterns (stripes, zigzags, and polka-dots). Others can be more complicated, such as the regular tiling of a plane, echos, and balanced binary branching.