Alternative: Single ICD-10 code reproduces the complete meaning of one ICD-9 code. Cluster: Multiple ICD-10 codes representing single ICD-9 code. At times it requires multiple ICD-10 codes combined to reproduce the complete meaning of one ICD-9 code. Mapping Types: "Single Code-to-Single Code", "Single Code-to-Cluster", "Cluster-to-Single Code". Note: More than one ICD-10 code (cluster) may be a valid translation of a given ICD-9 code. Which one of those ICD-10 codes (clusters) is the most correct translation must be determined based on the clinical case.