In econometrics, the seemingly unrelated regressions or seemingly unrelated regression equations model, proposed by Arnold Zellner in, is a generalization of a linear regression model that consists of several regression equations, each having its own dependent variable and potentially different sets of exogenous explanatory variables.

Unrelated Business Income Tax in the U.S. Internal Revenue Code is the tax on unrelated business income, which comes from an activity engaged in by a tax-exempt 26 U.S.C. 501 organization that is not related to the tax-exempt purpose of that organization.