  "How to generate a sentence" is the most critical and difficult problem in
all the natural language processing technologies. In this paper, we present a
new approach to explain the generation process of a sentence from the
perspective of mathematics. Our method is based on the premise that in our
brain a sentence is a part of a word network which is formed by many word
nodes. Experiments show that the probability of the entire sentence can be
obtained by the probabilities of single words and the probabilities of the
co-occurrence of word pairs, which indicate that human use the synthesis method
to generate a sentence.
