Background: Systems whose requirements change at a rate that necessitates adaptation without human intervention are called self-adaptive systems, and they have the ability to adjust their behavior autonomously at run-time in response to their environment’s evolution. Samples of applications that require self-adaptation include Smart home systems and environmental monitoring. However, self-adaptivity is often constructed in an ad-hoc manner. Methods: In this paper, the authors present a pattern-based specification language for self-adaptive systems. Its semantics are presented in terms of fuzzy logic. Thus, enabling a meticulous processing of requirements, in order to permit the formulation of self-adaptive requirements accurately, thereby facilitates the design of systems that are flexible and responsive to adaptation in a systematic manner. Results: To show the applicability and effectiveness of our language, the authors apply it to two case studies. One case study reviews the Smart fridge in ambient assisted living and the second case study is focused on an ambulance dispatching system using a developed support tool.