17. The system of claim 11 , wherein to form the topic cluster includes to: determine a first set of similar words comprising similar words of the seed word; add to the topic cluster a first set of one or more qualified first similar words from the first set of similar words, wherein the first set of one or more qualified first similar words at least meets a first similarity threshold with respect to the seed word; for a qualified similar word in the first set of one or more qualified similar words: determine a second set of similar words of the qualified similar word; add to the topic cluster a second similar word from the second set of similar words, wherein similarities between the second similar word and existing words in the topic cluster at least meet a second similarity threshold, and the second similar word is not found in the topic cluster prior to being added.
17. The system of claim 11 , wherein to form the topic cluster includes to: determine a first set of similar words comprising similar words of the seed word; add to the topic cluster a first set of one or more qualified first similar words from the first set of similar words, wherein the first set of one or more qualified first similar words at least meets a first similarity threshold with respect to the seed word; for a qualified similar word in the first set of one or more qualified similar words: determine a second set of similar words of the qualified similar word; add to the topic cluster a second similar word from the second set of similar words, wherein similarities between the second similar word and existing words in the topic cluster at least meet a second similarity threshold, and the second similar word is not found in the topic cluster prior to being added. 18. The system of claim 17 , wherein the first similarity threshold, the second similarity threshold, or both, are automatically selected.