cotype

Etymology
From.

Noun

 * 1)  A syntype or paratype.
 * 2)  A Banach space $$(X,\|\cdot\|)$$, such that, given a sequence of independent random variables from a Rademacher distribution, $$(\varepsilon_i)$$, and a rank $$q$$ in the range from 2 to infinity, there exists a finite constant $$C \geq 1$$ such that for all finite sequences $$(x_i) \in X$$, $$\mathbb{E}_{\varepsilon}\left[\left\|\sum\limits_{i=1}^n \varepsilon_i x_i\right\|^q \right]\geq \frac{1}{C^q}\left(\sum\limits_{i=1}^n \|x_i\|^q\right), \quad\text{if}\;2\leq q <\infty$$ or $$\mathbb{E}_{\varepsilon}\left[\left\|\sum\limits_{i=1}^n \varepsilon_i x_i\right\| \right]\geq \frac{1}{C}\sup\|x_i\|, \quad\text{if}\;q=\infty$$.