olemus
hulkade \(A\) ja \(B\) vahe on hulk \(A\backslash B\),
mille elemendid on hulga \(A\) kõik need elemendid,
mis hulka \(B\) ei kuulu, st
\(A\backslash B = \{a\in A\colon a\not\in B\}\)

ülevaateid
https://www.oxfordreference.com/view/10.1093/oi/authority.20110803100456845

https://mathworld.wolfram.com/SetDifference.html

https://en.wikipedia.org/wiki/Complement_(set_theory)#Relative_complement

https://proofwiki.org/wiki/Definition:Set_Difference