1. A core concept or principle that serves as the basis for a system, theory, or belief
The foundational idea of democracy is that power derives from the people.
A ideia fundamental da democracia é que o poder emana do povo.
2. A primary notion upon which other thoughts or structures are built
Mathematical axioms are foundational ideas that support all theorems.
Os axiomas matemáticos são ideias fundamentais que sustentam todos os teoremas.