Article 18 provides a comprehensive list of defined terms used throughout the Decision, ensuring legal precision. Key definitions include 'Acceptable Financial Accounting Standard', 'Adjusted Covered Taxes', 'Arm's Length Principle', and 'Constituent Entity'. It also provides detailed legal criteria for determining the 'Location' of entities and permanent establishments, and distinguishes between various types of entities such as Flow-through, Tax Transparent, Reverse Hybrid, and Hybrid entities. These definitions are harmonized with the OECD Pillar Two Model Rules to ensure cross-border consistency.