20. The system of claim 11 , wherein each score comprises a geometric mean of (1) the frequency of a plurality of n-grams appearing in the candidate sentence, and (2) the measure of commonality between the candidate sentence and the query.
11. A system for providing a natural language answer to a natural language question, the system comprising: an interface configured to receive, over a computer network, a query comprising a grammatical question; an interface configured to submit the query to a lookup engine; an interface configured to receive initial search results from the lookup engine, the initial search results comprising a plurality of documents; a processor configured to identify, in the plurality of documents, a plurality of candidate sentences; a processor configured to calculate a frequency of a plurality of n-grams appearing in the plurality of candidate sentences, wherein n ranges at least from 1 to 2; a processor configured to calculate, for each candidate sentence, a measure of commonality between the candidate sentence and the query; a processor configured to assign, to each candidate sentence, a score, wherein the score comprises (1) the frequency of a plurality of n-grams appearing in the candidate sentence, and (2) the measure of commonality between the candidate sentence and the query; a processor configured to sort the candidate sentences according to score, whereby a rating of candidate sentences is produced; and an interface configured to send, over a computer network, a reply to the query, the reply comprising at least a top candidate sentence from the rating of candidate sentences.