The customization of a natural language interface to a certain application, domain or knowledge base still represents a major effort for end users given the current state-of-the-art. In this article, we present our natural language interface ORA-KEL, describe its architecture, design choices and implementation. In particular, we present ORAKEL's adaptation model which allows users which are not familiar with methods from natural language processing (NLP) or formal linguistics to port a natural language interface to a certain domain and knowledge base. The claim that our model indeed meets our requirement of intuitive adaptation is experimentally corroborated by diverse experiments with end users showing that non-NLP experts can indeed create domain lexica for our natural language interface leading to similar performance compared to lexica engineered by NLP experts.