1. A method of determining a combination of terms that represents subject matter of a natural language sentence, the method comprising the steps of: a computer determining respective numbers of words from a beginning of the sentence to respective terms in the sentence that match terms in the combination of terms; the computer dividing the sentence in a multiplicity of natural language phrases including a complex phrase and first and second simple phrases extracted from the complex phrase, the complex phrase being less than an entirety of the sentence; and based in part on (a) the respective numbers of words from the beginning of the sentence to respective terms in the sentence that match terms in the combination of terms, (b) whether all terms of the combination are contained in the first and/or second simple phrases, and (c) whether all terms of the combination are contained in the complex phrase but not contained in the first and/or second simple phrases, the computer determining how well the combination of terms represents the subject matter of the sentence.