Definition:Ideal


 * Ring Theory:
 * Ideal of Ring:
 * Left Ideal of Ring
 * Right Ideal of Ring


 * Order Theory:
 * Ideal (Order Theory)


 * Join Semilattice:
 * Join Semilattice Ideal


 * Lattice Theory:
 * Lattice Ideal


 * Physics:
 * Ideal (Physics)