13. A system, comprising: one or more processors; and memory having instructions stored thereon, the instructions, when executed by one or more processors, comprising: receiving a search query, the search query associated with a user identifier; receiving a ranked list of related search queries for the received search query, the related search queries being suggested alternate queries for the search query and ranked according to a first order; accessing a profile tree associated with the user identifier and including a hierarchy of nodes, the hierarchy of nodes including a root node and a plurality of child nodes, each child node descending from the root node or another child node, the profile tree defining a plurality of levels, each level including child nodes that descend from the root node at a same depth, and each node of the profile tree representing a respective topic that is derived from search history data associated with the user identifier, and each node of the profile tree corresponding to at least one of a term or a phrase, and wherein the terms and phrases of the profile tree correspond to the nodes of the profile tree according to the respective topics to which the search terms and phrases belong; for each of the related search queries: identifying in the profile tree one or more nodes that match the related search query; determining the respective levels of the one or more nodes that match the related search query; determining a respective child count for each of the one or more nodes that match the related search query, the child count for each node being proportional to a number of child nodes descending directly from the node and a number of child nodes descending indirectly from the node; and deriving a respective relevance score for the related search query based on the respective levels of the one or more nodes that match the related search query and the respective child counts of the one or more nodes that match the related search query, wherein the relevance score is directly proportional to depths of the respective levels of the one or more nodes that match the related search query, and is inversely proportional to the respective child counts of the one or more nodes that match the related search query; adjusting the rank of at least one of the related search queries in the list based on the respective relevance scores of the related search queries so that the search queries are ranked according to a second order different from the first order; and providing suggested query data to a client device associated with the user identifier, the suggested query data operable to cause the client device to present a plurality of top-ranked related search queries according to the second order.
13. A system, comprising: one or more processors; and memory having instructions stored thereon, the instructions, when executed by one or more processors, comprising: receiving a search query, the search query associated with a user identifier; receiving a ranked list of related search queries for the received search query, the related search queries being suggested alternate queries for the search query and ranked according to a first order; accessing a profile tree associated with the user identifier and including a hierarchy of nodes, the hierarchy of nodes including a root node and a plurality of child nodes, each child node descending from the root node or another child node, the profile tree defining a plurality of levels, each level including child nodes that descend from the root node at a same depth, and each node of the profile tree representing a respective topic that is derived from search history data associated with the user identifier, and each node of the profile tree corresponding to at least one of a term or a phrase, and wherein the terms and phrases of the profile tree correspond to the nodes of the profile tree according to the respective topics to which the search terms and phrases belong; for each of the related search queries: identifying in the profile tree one or more nodes that match the related search query; determining the respective levels of the one or more nodes that match the related search query; determining a respective child count for each of the one or more nodes that match the related search query, the child count for each node being proportional to a number of child nodes descending directly from the node and a number of child nodes descending indirectly from the node; and deriving a respective relevance score for the related search query based on the respective levels of the one or more nodes that match the related search query and the respective child counts of the one or more nodes that match the related search query, wherein the relevance score is directly proportional to depths of the respective levels of the one or more nodes that match the related search query, and is inversely proportional to the respective child counts of the one or more nodes that match the related search query; adjusting the rank of at least one of the related search queries in the list based on the respective relevance scores of the related search queries so that the search queries are ranked according to a second order different from the first order; and providing suggested query data to a client device associated with the user identifier, the suggested query data operable to cause the client device to present a plurality of top-ranked related search queries according to the second order. 18. The system of claim 13 , wherein for each of the related search queries, the one or more nodes that match the related search query each represents a respective topical category that includes a concept represented by terms of the related search query.