1. A computer-storage medium storing computer-executable instructions that, when executed, perform a method of determining a document score, which suggests a relevance of a document to a search query, the method comprising: receiving the search query; parsing the search query into a first n-gram having a first weight and a second n-gram having a second weight, wherein the first weight quantifies an importance of the first n-gram to the search query and the second weight quantifies an importance of the second n-gram to the search query; determining that the first weight and the second weight satisfy a threshold weight criterion, wherein an n-gram is not used to determine the document score when a weight of the n-gram does not satisfy the threshold weight criterion; identifying a first equivalent subject that is semantically similar to the first n-gram and a second equivalent subject that is semantically similar to the second n-gram, wherein the first n-gram and the first equivalent subject comprise a first subject group and the second g-gram and the second equivalent subject comprise a second subject group; and determining the document score of the document, wherein the document score is comprised of a first subject-group score and a second subject-group score, and wherein both subject-group scores are calculated using both a subject frequency, which includes a number of times a respective n-gram is found in the document, and an equivalent-subject frequency, which includes a number of times a respective equivalent-subject is found in the document.