We present an extension to the definition of a concept in an ontology that allows an agent to simultaneously communicate with a group of agents that might have different understandings of some concepts. We also provide a way to learn such non-unanimous concepts by using a method for learning concepts from a group of teachers. The general idea of non-unanimous concepts is to use the teachers to identify the core of a concept everyone agrees on and what else at least some of the teachers think belongs into the concept. The learning agent also decides what belongs to the concept for itself and whenever it needs to communicate with a group of other agents and needs to be precise it makes use of these three concept aspects by providing additional example objects for what might be misunderstood.