Business English and academic English may perhaps be thought of as areas of language use requiring precision of expression and a quest for specific and unambiguous meaning. However, corpus evidence shows that both types of language, in their spoken contexts, exhibit noticeable use of the kinds of vague expressions found in everyday conversation. In this lecture, I focus on one type of vagueness: "vague category marking" (VGM). This feature involves mention of an example or examples of something followed by reference to a broad, ad hoc category of which the chosen examples are seen as typical. References to categories commonly involve expressions such as "or whatever, and so on, or something (like that)." In both business and academic English, vague category marking is an important projection of shared knowledge and shared identities. In business, vagueness is also a useful tool in delicate negotiations. In academic English, vague categories refer to bodies of assumed shared knowledge and are crucial in the pedagogic process of grafting new knowledge onto old. Subtle differences are drawn out by different types of vague category markers. I conclude with some implications for teaching in these specialised areas.