Sentence:  Swadesh , and therefore Hoijer , felt compelled to omit all terms denoting species or even genera ( fox , vulture , salmon , yellow pine , manzanita ) ; their classes of animal and plant <WSD>terms</WSD> are restricted to generalizations or recurrent parts ( fish , bird , tree , grass , horn , tail , bark , root ) . 
Meaning of the word marked with <WSD> tags:  a word or expression used for some particular thing