Sentence:  Although it is common knowledge today that a great many linguistic categories are, indeed, <WSD>prototype</WSD> categoriesnb..., a number of linguists still perceive grammatical categories as being classical in their naturenb.... These linguists are reluctant to accept the idea that prototypicality might be relevant to grammar and that grammatical categories, like all other categories, can also display <WSD>prototype</WSD> effects. 
Meaning of the word marked with <WSD> tags:  An instance of a category or a concept that combines its most representative attributes.