 Non-realist and antirealist semantics for theoretical terms are motivated by the presumption that the problem of theoretical terms has no satisfying realist solution. What does a non-realist semantics of theoretical terms look like? The view that theoretical entities are mere fictions often figures in realist portrays of antirealism. This view is hardly seriously maintained by any philosopher of science in the twentieth century. If one were to devise a formal or informal semantics for the view that theoretical entities are mere fictions, a purely descriptive account seems most promising. Such an account could in particular make heavy use of the Fregean notion of sense. For one important motivation for introducing this notion is to explain our understanding of expressions like ‘Odysseus’ and ‘Pegasus’.