1. A basic, fundamental rule that forms the foundation of a system, subject, or discipline
One of the elementary rules of mathematics is that you must follow the order of operations.
Uma das regras elementares da matemática é que você deve seguir a ordem das operações.
2. A simple principle or guideline that is taught at the beginning level of instruction
The elementary rules of grammar include subject-verb agreement.
As regras elementares da gramática incluem a concordância entre sujeito e verbo.