===== Union =====
==== Set ====
| @#55CCEE: context     | @#55CCEE: $X,Y$ ... set |
| @#FFBB00: definiendum | @#FFBB00: $ x\in X \cup Y $ |
| @#55EE55: postulate   | @#55EE55: $ x\in X\lor x\in Y $ |

==== Discussion ====
The 2-ary set construction $ X \cup Y $ is commutative and idempotent.

Notice that $ X \cup \emptyset = X$.

The union and [[intersection]] are associative and distributive with respect to another.
=== Reference ===
Wikipedia: [[http://en.wikipedia.org/wiki/Complement_%28set_theory%29|Union]]
==== Parents ====
=== Context ===
[[Sets]]