Given an indexed collection of sets [itex]A_x[/itex] the disjoint union of these sets can be thought of as the ordinary union of the sets [itex] \{ x \} \times A_x [/itex] for all(adsbygoogle = window.adsbygoogle || []).push({}); x. That is, it is the set of all pairs [itex](x, a)[/itex] where [itex]a \in A_x[/itex].

(Correct me at this point if my understanding of disjoint union is wrong.)

Does this have any practical difference from set of all [itex]A_x[/itex] ?

Denote the set of index values by X. That is, is there any practical difference between [itex] \{ (x, a) | x \in X \wedge a \in A_x \}[/itex] versus [itex]\{ A_x | x \in X \}[/itex] ?

**Physics Forums | Science Articles, Homework Help, Discussion**

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# I How does a disjoint union differ from a set of sets?

Have something to add?

Draft saved
Draft deleted

**Physics Forums | Science Articles, Homework Help, Discussion**