With massive investments in health-related research, in addition to investments in the management and delivery of healthcare and public health services, there is a growing focus on the impact of health research to explore and explain the consequences of these investments and inform strategic planning. Increased focus to the usability and effect of health research reflects relevance, with research funders increasingly using relevance assessment as a decision-making input. Relevance is a synonym for or predictor of effect, an essential prerequisite or stage in reaching it, or a unique goal of the research work. The basic goal of this work is to improve our understanding of research relevance, with specific goals of (1) unpacking research relevance from both theoretical and practical perspectives, and (2) outlining essential assessment concerns. The importance of research relevance in justifying research spending and directing strategic research planning appears to be growing. However, in the health research community, relevance has been mostly unspoken, relying on unexplained interpretations of value, fit, and impact potential. While it appears that research relevance is a required condition for effect - a process or component of efforts to make rigorous research accessible - relevance is ultimately distinct from research impact. To assess the total value and impact of a wide range of individual and group research efforts and investments, careful and explicit assessment of research relevance is required. This paper explains how research relevance assessments (1) orient to, capture, and compare research versus non-research sources, (2) consider both instrumental and non-instrumental uses of research, (3) accommodate dynamic temporal-shifting perspectives on research, and (4) align with an inter subjective understanding of relevance.