Sentence:  There <WSD>are</WSD> more stems per item in Athabascan , which expresses the fact that the Athabascan languages have undergone somewhat more change in diverging from proto Athabascan than the Yokuts languages from proto Yokuts . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)