Word frequency-rank relationship in tagged texts

We analyze the frequency-rank relationship in sub-vocabularies corresponding to three different grammatical classes ({\em nouns}, {\em verbs}, and {\em others}) in a collection of literary works in English, whose words have been automatically tagged according to their grammatical role. Comparing with a null hypothesis which assumes that words belonging to each class are uniformly distributed across the frequency-ranked vocabulary of the whole work, we disclose statistically significant differences between the three classes. This results point to the fact that frequency-rank relationships may reflect linguistic features associated with grammatical function.