A FAIR-compliant metadata vocabulary (MV), the Library Transaction Ontology (LTO), is designed and developed for representing and managing library transaction data (LTD), including circulation, interlibrary loan, hold requests, and fiscal information. Our investigation revealed that despite significant focus on bibliographic and authority data, no standardized vocabulary exists for LTD, resulting in data loss, mapping errors, and interoperability challenges during system migration and integration. LTO supports machine processing and automated reasoning for data-driven decision making. Additionally, it supports interoperability across heterogeneous library platforms by providing mappings for the circulation metadata of multiple Library Management Systems (LMS), including Koha, Virtua, Evergreen, SOUL, etc. It is also compliant with the Library of Congress's (LOC) BIBFRAME model and extends the bibliographic Linked Data (LD) framework to support the standardized representation of library transaction LD. LTO?s elements were validated through expert evaluation by LIS professionals, and its effectiveness in information processing and retrieval was successfully assessed. @en