All: Is there an established name for the following propery of a relation R on a set X: for x st x \in X ex y st y \in X & ([x,y] \in R or [y,x] \in R) or equivalently: dom R U rng R = X Some names that come to mind for such a property: semi-total, semi-connected. Is there a better name? -- Piotr Rudnicki