This paper works toward a category definition for advertising in generative AI. A category definition in this sense develops a structure that holds from the problems that arise when advertising enters GenAI: a reference point, principles, and classifications proposed on that basis. Because GenAI produces content in the moment it could be altered by advertising, which is an integrity problem. But even if advertising does not alter the output of a GenAI system, a trust problem arises. This does not only affect users, but also advertisers who cannot prove that they did not influence the content. Since the content did not exist beforehand, addressing this at the level of content is not straightforward. The structural solution is to make the relationship between the GenAI system and advertising addressable through coupling advertising to a compute unit as a reference point. As advertising can draw on semantic sources the compute unit contains, a classification and notation are proposed. Situating the concept in the research literature remains open.