Barriers to entry are factors that prevent or hinder companies from entering a specific market. Entry barriers may result, for instance, from a particular market structure (for example, sunk cost industry, brand loyalty of consumers to existing products) or the behaviour of incum- bent firms. It is important to add that governments can also be a source of entry barriers (such as through licensing requirements and other regulations).
Source: Glossary of terms used in EU competition policy, Antitrust and control of concentrations, European Commission, 2002