In one embodiment, searching documents includes generating a query conceptual graph for a search query. The query conceptual graph has graph terms representing concept types. A set of conceptually similar terms is identified for each graph term, and the set is mapped to the concept type represented by the graph term. Documents are searched in accordance with the set of conceptually similar terms. In another embodiment, selecting a document includes determining documents that satisfy a search query expressed as a query conceptual graph. A document conceptual graph that has graph terms representing concept types is generated for each document. A set of conceptually similar terms is identified for each graph term, where the set is mapped to the concept type represented by the graph term. A document is selected if terms of the sets associated with the document match terms associated with the query conceptual graph.