First-order refers to a basic level of understanding or analysis in various fields, such as logic, mathematics, and philosophy. In logic, first-order logic involves quantifying over individual elements, allowing for statements about objects and their relationships. It is foundational for more complex systems, such as second-order logic, which includes quantification over sets or properties. In mathematics, first-order equations are the simplest type of equations, involving only the first power of the variable. These equations can often be solved using straightforward algebraic methods. Overall, first-order concepts serve as building blocks for more advanced theories and applications in different disciplines.