Pattern Language is a method of describing good design practices for a particular field in a structured and coherent way. It was first introduced by architect Christopher Alexander and his colleagues in their book "A Pattern Language," which was published in 1977. This book describes a series of interconnected patterns that can be used to create a wide range of structures, from buildings to software systems. Each pattern describes a problem that occurs over and over again in a specific context, and presents a solution that can be applied in that context to solve the problem.

"A Pattern Language" is a book written by Christopher Alexander and published in 1977. It is a guide to creating functional and aesthetically pleasing designs for various aspects of everyday life, from the layout of a city to the design of a single room. The book is organized into a series of interrelated "patterns," each of which describes a problem and presents a solution in the form of a specific design. The patterns are intended to be applied together in a hierarchy, with higher-level patterns relying on the solutions provided by lower-level patterns. The book is notable for its holistic approach to design and its emphasis on the importance of human experience and needs in the built environment.

Wiki:

A pattern language is an organized and coherent set of patterns, each of which describes a problem and the core of a solution that can be used in many ways within a specific field of expertise. The term was coined by architect Christopher Alexander and popularized by his 1977 book A Pattern Language.