Definition of "cotype"

(taxonomy, dated) A syntype or paratype.  examples

(functional analysis) A Banach space ( X , ‖ ⋅ ‖ ) , such that, given a sequence of independent random variables from a Rademacher distribution, ( ε i ) , and a rank q in the range from 2 to infinity, there exists a finite constant C ≥ 1 such that for all finite sequences ( x i ) ∈ X , E ε [ ‖ ∑ i = 1 n ε i x i ‖ q ] ≥ 1 C q ( ∑ i = 1 n ‖ x i ‖ q ) , if 2 ≤ q < ∞ or E ε [ ‖ ∑ i = 1 n ε i x i ‖ ] ≥ 1 C sup ‖ x i ‖ , if q = ∞ .  examples