Fairness in assessment is seen as increasingly important but there is a need for greater clarity in use of the term 'fair'. Also, fairness is perceived through a range of 'lenses' reflecting different traditions of thought. The lens used determines how fairness is seen and described. This article distinguishes different uses of 'fair' which have relevance to assessment. It identifies some of the 'lenses' used to examine fairness in assessment and suggests a framework of questions which can be applied to each lens. It then applies this approach to the lens of theoretical writing about assessment measurement. It describes a broad consensus among measurement theorists in their account of fairness and critiques aspects of that view.