[Progress in research of the definition of multimorbidity]

With the rapid global population aging, multimorbidity is becoming a more serious public health problem, to which medical researchers have paid close attention. A standardized definition of multimorbidity is essential for relevant research. However, there is a lack of consensus on the definition of multimorbidity, which makes it difficult to compare results among studies and replicate important findings. Based on the conceptual comparison, this paper summarizes the key dimensions of the definition of multimorbidity, including the number and types of conditions, the granularity of classification, methods for obtaining outcomes, and settings and objectives of research. It also discusses the inherent relationships among the dimensions and their impact on research results, and introduces the characteristics of the commonly used condition lists in current multimorbidity definition research. By suggesting areas for improvement in the multimorbidity definition system, it aims to enhance the understanding of multimorbidity research and achieve consensus on the definition, thereby facilitating further multimorbidity research.