Which appendix of the Air Navigation Order defines the terms used in the ANO?

The correct answer is the first appendix of the Air Navigation Order, which defines the terms used within the ANO. This appendix serves as a reference point for understanding the specific terminology that appears throughout the regulations, ensuring that pilots and aviation professionals have a consistent understanding of key concepts. Clear definitions are crucial for compliance with aviation laws and safe operations in the airspace since they help eliminate ambiguity.

The other appendices serve different purposes; for instance, some may outline regulations regarding specific aviation practices or technical requirements rather than defining terms. This distinction highlights the fundamental role that the first appendix plays in the context of the entire Air Navigation Order.