Clarity in terminologies is vital in science. The term ‘mixotroph’ has a long history and is defined in Henderson’s dictionary of biology as ‘an organism using an inorganic compound as energy source and an organic compound as carbon source’. However, while the common exemplar 'mixotroph’, the Venus flytrap, feeds for nutrients and not C, phytoplankton that consume dissolved free amino acids for C, energy and N via osmotrophy are often not viewed as mixotrophs even though by definition they are. In contrast, photo-phagotrophic protists are always referred to as mixotrophic, irrespective of why they feed. Ecologically, there is a critical distinction between protist plankton that are mixotrophic via osmotrophy versus via phagotrophy; the latter play a vital role in trophic dynamics through removal of prey/competitors. To provide a clear distinction between such organisms the term ‘mixoplankton’ was proposed, with a concise definition – ‘protist plankton that are photo-phago-osmo-trophic’. Mixoplankton are thus all mixotrophs, but not all planktonic mixotrophs are mixoplankton. Importantly for science, ‘mixoplankton’ also sets these protists apart from the photo-osmo-mixotrophic ‘phytoplankton’ and heterotrophic ‘zooplankton’. In moving away from a plant-animal dichotomy in marine ecology the term mixoplankton provides concise clarity. It provides a tool for us to redefine the core underpinning of marine science, to perform keyword searches, to differentiate database entries, model descriptions, and to reflect the biogeochemical and ecological consequences.