| Zero degree homogeneous | Homogeneous of degree zero. |
| Zero profit | A situation in which profit in an industry is zero, usually as a result of free entry and exit. It may, if firms are not identical, refer only to the marginal firm. And it always means zero excess profit, not that all returns to capital invested in the industry are zero. |
| Zero substitution | An elasticity of substitution of zero. In a production function, this means a Leontief technology. |
| Zero sum game | A game in which the payoffs to the players add up to zero, so that a gain for one is necessarily equaled by loss to others. Contrasts with positive sum game. |