Commercial practice of conditioning the sale of one product on the purchase of another product. If tying is not objectively justified by the nature of the products or their commercial usage, such practice may restrict competition. Economic theory suggests that a firm which enjoys market power in one market (tying market) may, under certain conditions, be able to lever this market position or dominance into another market (tied market), squeeze competitors out of this second market and then raise prices above the competitive level. In a competition analysis perspective, the main negative effect of tying on competition is, therefore, possible foreclosure on the market of the tied product. In addition tying may lead to higher prices for both the tying and the tied product.
Source: Glossary of terms used in EU competition policy, Antitrust and control of concentrations, European Commission, 2002