A metamodel is a high-level model that defines the structure and constraints of other models. Some synonyms for metamodel include conceptual model, domain model, modeling framework, and schema. Conceptual models represent abstract concepts in a domain, while domain models capture the data and rules specific to a domain. Modeling frameworks provide a set of tools and conventions to create models and are designed to be extensible. A schema is a description of a structured format for representing data that includes definitions of entities and their relationships. Each of these synonyms helps to convey the central idea of a metamodel--that it defines the structure and constraints of other models in a specific domain.