2000), here Count(w) refers to the total frequency of the character string corresponding to the word w in the training corpus, which is counted from word lattice or from raw corpus of the relevant training data, and Count(pttn(w)) is the frequency of the word w given its certain pattern pttn(w) , which can be counted directly from a segmented corpus.
if we encounter an unknown word in process of counting, we firstly segment it into a sequence of component words using the forward maximum match method, and then count the relevant pattern frequency for each component word.