11. The media of claim 9 , wherein modifying the probability function to adjust the probability includes modifying the probability function to increase the probability when the disjunction of the one or more n-grams corresponds semantically to the concept defined by the words in the dictionary.
9. One or more hardware computer-storage media having embodied thereon computer-usable instructions that, when executed, facilitate a method of feature completion for machine learning, the method comprising: storing a first set of data items, wherein each data item includes a text stream of words; accessing a dictionary, wherein the dictionary includes a list of words that define a concept usable as an input feature for training a machine-learning model to score data items with a probability of being a positive example or a negative example of a particular class of data item; and training the machine-learning model with the dictionary as an input feature, wherein the training includes, for each data item in the first set of data items: for a first word position in the text stream within the data item, examining a window of text centered at a second word position in the text stream, wherein the window of text includes one or more words, utilizing a probability function to calculate a probability of the presence, at the first word position, of a disjunction of one or more n-grams that correspond semantically to the concept defined by the words in the dictionary, based on the one or more words in the window of text, determining an actual presence or absence, at the first word position, of a disjunction of one or more n-grams that correspond semantically to the concept defined by the words in the dictionary, wherein the determining comprises determining one or more of: whether any words from a given list appear at the center of a window of text around the given word position in which center words in the window of text have been removed, a presence or absence of a verb in the window, a presence or absence of a noun followed by an adjective, or a number of occurrences of a given word in the window, and modifying the probability function to adjust the probability in a positive or negative direction based on the determined actual presence or absence of the disjunction of one or more n-grams that correspond semantically to the concept defined by the words in the dictionary.