In the literature (1) and in commercial advertising, one can often find material descriptions of chromatographic retention that use the terms hydrophilic interaction liquid chromatography (HILIC) and aqueous normal phase (ANP) in such a manner that they can be construed to be identical. However, in reality, there should be (and there is) a real difference between these two modes of retention and the types of columns that achieve them. A more precise definition of ANP and HILIC is proposed here that will enable chromatographers to distinguish between the two mechanisms and select columns suitable for particular applications.