pattern, n
1. 'The original proposed to imitation; the archetype; that which is to be copied; an exemplar' (J.); an example or model deserving imitation; an example or model of a particular excellence.
2. Anything fashioned, shaped, or designed to serve as a model from which something is to be made; a model, design, plan, or outline.

-- Oxford English Dictionary, 2nd edn

The elements of this language are elements called patterns. Each pattern describes a problem which occurs over and over again in our environment, and then describes the core of the solution to that problem, in such a way that you can use this solution a million times over, without ever doing it the same way twice.

Alexander et al. A Pattern Languge, p x. 1977

A pattern is a particular arrangement of elements that constitute a model to be used or emulated. Patterns are patterns if they can do something, if they can cause something to occur with some regularity. ... a pattern [is] an arrangement that expresses a reproducible and meaningful relationship between relatively independent components.

Cohen. Tending Adam's Garden, §131. 2000