19. The computing device of claim 17 , wherein the word clustering comprises: creating a language model from a corpus of text; computing a pair-wise similarity between nouns, verbs, and adjectives or adverbs in the corpus of text; creating a list of similar words for each word in the language model; matching the advertising text with a word in the language model and the list of similar words corresponding to the word; and associating the advertisement with the sentence, based on the matching, such that a word in the sentence is in the list of similar words.
17. The computing device of claim 16 , wherein the associating is based at least in part upon at least one of user logs, a word clustering, or bidding rules.