A pattern is a form, template, or model (or, more abstractly, a set of rules) which can be used to make or to generate things or parts of a thing, especially if the things that are generated have enough in common for the underlying pattern to be inferred or discerned, in which case the things are said to exhibit the pattern. The detection of underlying patterns is called pattern recognition.

The simplest patterns are based on repetition: several copies of a single template are combined without modification. For example, in aviation, a "holding pattern" is a flight path which can be repeated until the aircraft has been granted clearance for landing.

Pattern recognition is more complex when templates are used to generate variants. For example, in English, sentences often follow the "N-VP" (noun - verb phrase) pattern, but some knowledge of the English language is required to detect the pattern.

Pattern recognition is studied in many fields, including psychology, ethology, and computer science.

Some patterns (for example, many visual patterns) may be directly observable through the senses.

Some patterns are named. Simple decorative examples are stripes and zigzags. Further examples include the regular tiling of a plane , echoes, and balanced binary branching.

The planets of our solar system are caught in an incredibly ancient pattern by the gravity of the Sun. The planets have been following their (very predictable) elliptical orbits for billions and billions of years. There is certainly a recognizable pattern/cycle there.

Fractals are mathematical patterns. Naturally occurring patterns obey certain principles also found in fractals, for example self-similarity. Even though self-similarity in nature is only approximate and stochastic, integral measures describing fractal properties can also be applied to natural "fractals" like coastal lines , tree shapes , etc. (see fractal geometry). While the outer appearance of self-similar patterns can be quite complex, the rules needed to describe or produce their formation can be extremely simple (e.g. Lindenmayer systems for the description of tree shapes).

In addition to static patterns there may be patterns of movement such as oscillation.

Patterns in nature

• Sea shells, Sand Dollars
• Sand dunes, Grand Canyon
• Tree branches , ferns, coastal lines, clouds

Patterns in art

• Modern art: Mondrian, Op Art
• Impressionism: Pointillism
• Performance Art: Crop circles

Patterns in science and mathematics

• Fractals
• Crystals
• Penrose tilings

Quotation

"Art is the imposing of a pattern on experience, and our aesthetic enjoyment is recognition of the pattern." Alfred North Whitehead (1861-1947), English philosopher and mathematician. Dialogues, June 10, 1943.

Other senses of "pattern"

Sometimes pattern is defined as the repetition of a template, or as the abstract quality shared by products produced from a template according to a set of rules.

In machine learning, a pattern is a non-null finite sequence of constant and variable symbols. The language of a pattern is the set of strings generated by substituting variables in the pattern by non-null sequences of constant symbols.

"Pattern" may also refer to a (generally non-rigid) routine as in a person developing a certain pattern of life. See Ethnomethodology for the science of such regular routines. See also Cycle and List of cycles.

In Ireland, "pattern" can also refer to devotional practices associated with a patron saint.

See also

• Design pattern (architecture)
• Design pattern (computer science)
• Pattern (devotional)
• Pattern recognition
• Regular expressions
• DNA motifs