Abstract: A natural language parser determines part-of-speech probabilities by using a dictionary or other lexicon as a source for the part-of-speech probabilities. A machine-readable dictionary is scanned, word-by-word. For each word, the number of senses listed for the word and associated with a part of speech are counted. A part-of-speech probability is then computed for each part of speech based upon the number of senses counted. The part-of-speech probability is indicative of how likely the word is to assume a particular part of speech in a text. The most probable parts of speech are then used by a parser during the first parse of an input string of text to improve the parser's accuracy and efficiency.