11. A system for classifying a user input, comprising: a user interface to receive a user input of Roman characters from one or more users and to provide possible Chinese queries that correspond to the user input; and one or more computers including a pinyin classifier configured to: identify a first ambiguous word in the user input, the first ambiguous word being identified as a string of the Roman characters that is both a non-pinyin word written in the Roman characters and a valid pinyin input of one or more pinyin syllables that correspond to an entry in a Chinese dictionary; determine that each of one or more words adjacent to the first ambiguous word, are classified as belonging to one of a pinyin context or belonging to a non-pinyin context; classify the first ambiguous word as one of a pinyin input or a non-pinyin word, the classification of the first ambiguous word being based on the classification of the one or more adjacent words, the ambiguous word being classified as a pinyin input in response to the one or more words adjacent to the first ambiguous word being classified as belonging to the pinyin context, and the first ambiguous word being classified as a non-pinyin word in response to the one or more words adjacent to the first ambiguous word being classified as belonging to the non-pinyin context; identify a second ambiguous word in the user input; determine that the second ambiguous word is located between a first word that is classified as belonging to the pinyin context and a second word that is classified as belonging to the non-pinyin context; determine a probability that the second ambiguous word corresponds to an entry in a Chinese dictionary; and classify the second ambiguous word based on the probability, the second ambiguous word being classified as a pinyin input when the probability meets a threshold probability.
11. A system for classifying a user input, comprising: a user interface to receive a user input of Roman characters from one or more users and to provide possible Chinese queries that correspond to the user input; and one or more computers including a pinyin classifier configured to: identify a first ambiguous word in the user input, the first ambiguous word being identified as a string of the Roman characters that is both a non-pinyin word written in the Roman characters and a valid pinyin input of one or more pinyin syllables that correspond to an entry in a Chinese dictionary; determine that each of one or more words adjacent to the first ambiguous word, are classified as belonging to one of a pinyin context or belonging to a non-pinyin context; classify the first ambiguous word as one of a pinyin input or a non-pinyin word, the classification of the first ambiguous word being based on the classification of the one or more adjacent words, the ambiguous word being classified as a pinyin input in response to the one or more words adjacent to the first ambiguous word being classified as belonging to the pinyin context, and the first ambiguous word being classified as a non-pinyin word in response to the one or more words adjacent to the first ambiguous word being classified as belonging to the non-pinyin context; identify a second ambiguous word in the user input; determine that the second ambiguous word is located between a first word that is classified as belonging to the pinyin context and a second word that is classified as belonging to the non-pinyin context; determine a probability that the second ambiguous word corresponds to an entry in a Chinese dictionary; and classify the second ambiguous word based on the probability, the second ambiguous word being classified as a pinyin input when the probability meets a threshold probability. 12. The system of claim 11 , wherein the pinyin classifier is further configured to classify the one or more words adjacent to the first ambiguous word as belonging to the pinyin context when the one or more words adjacent to the first ambiguous word are valid pinyin words and not valid non-pinyin words.