AbstractTerminology matters ‐ as Lakoff emphasised, words and phrases evoke powerful images and frames of understanding. It is for that reason that we need to discern and use appropriately the term complex/complexity in the health science/professional/policy domain. Complex is the fashionable term used when in reality one means ‘complicated’, ‘difficult to understand’ or ‘multiple simultaneous actions’. However, this is not what complex means. The Latin term means ‘entwined/interwoven’ ‐ a structural characteristic describing systems. Complexity arises from the interactions between structurally connected entities ‐ a functional characteristic of a system.The basis of scientific rigor is a clear understanding of a discipline's epistemology. Complexity refers to the emergence of outcomes from the interactions of a system's constituent components (and thus has nothing in common with the colloquial meaning of complicatedness).