Join Semilattice

束論 Lattice_Theory https://en.wikipedia.org/wiki/Semilattice https://ja.wikipedia.org/wiki/結びと交わり

• Idempotent Law (冪等性): $a\vee a=a$
• Associative Law (結合性): $a\vee (b\vee c)=(a\vee b)\vee c$
• Commutative Law (可換性): $a\vee b=b\vee a$