olemus
hulkadest \(A_1, A_2, A_3, \ldots\) moodustatud hulk
\(A_1\cup A_2\cup A_3\cup \ldots = \cup_i A_i\) ,
mis koosneb hulkade \(A_1, A_2, A_3, \ldots\)
kõigist elementidest, st
\(\cup_i A_i = \{a\colon\; \exists i\colon a\in A_i \}\)

Wiktionary:
union
(countable, set theory) the set containing all of the elements of two or more sets

ülevaateid
https://en.wikipedia.org/wiki/Union_(set_theory)

https://www.cuemath.com/algebra/union-of-sets/

https://courses.lumenlearning.com/math4libarts/chapter/union-intersection-and-complement/

vt ka
- hulkade ühisosa