| − | In [[math]]ematics, a '''union''' of sets is a [[set]] of elements that belong only to the sets. The union of sets A and B is denoted A ∪ B and is formally defined as A ∪ B = {x|xϵA OR xϵB}. | + | In [[math]]ematics, a '''union''' of sets is a [[set]] of elements that belong only to at least one of the sets. The union of sets A and B is denoted A ∪ B and is formally defined as A ∪ B = {x|xϵA OR xϵB}. |