Which of the following best defines the term "fundamental"?

The term "fundamental" refers to something that is basic and essential, serving as the foundation for other ideas or concepts. In various contexts, it denotes the core principles upon which systems or theories are built. For instance, in mathematics, fundamental concepts such as numbers and operations are crucial for understanding more complex problems. Similarly, in philosophy, fundamental questions address the essence of existence and reality. Therefore, the definition that captures this essence accurately aligns with the idea of being basic and essential, indicating that it is something necessary for comprehension or functioning within a specific context. The other options, which suggest meanings related to secondary importance or complexity, do not align with the inherent nature of "fundamental."