Pattern languages are an approach to provide common knowledge in an easily accessible way. They were originally invented in the 70s and first applied in civil and architectural design. During the last decade the approach has been commonly applied in the software community and gained a strong influence on many fields within computer science. In engineering design as well as Product Lifecycle Management (PLM) pattern languages have yet not been applied. This paper introduces the concept of pattern languages and describes approaches to apply pattern languages to PLM to develop a cohesive PLM theory integrating the several subareas of PLM.