In set theory, König's theorem states that if the axiom of choice holds, I is a set, κ i {\displaystyle \kappa _{i}} and λ i {\displaystyle \lambda _{i}} are cardinal numbers for every i in I, and κ i < λ i {\displaystyle \kappa _{i}<\lambda _{i}} for every i in I, then ∑ i ∈ I κ i < ∏ i ∈ I λ i. Wikipedia