"Semantics" is very trendy in today's literature in content-based image retrieval, but, in most of the proposed methods, it corresponds merely to giving a name belonging to natural language to a cluster of low-level features. In the talk, the different aspects of "semantics" as a whole and independent field of linguistic research will be exposed. Then, the main different ways which have been explored to use semantics for image annotation and image retrieval will be detailed. Then, a method for semantic annotation of satellite images, making use of semantic relationships, will be detailed. This method is based on the duality of a semantic network and a stochastic model and makes intensive use of semantics.