Sentence:  Thus, the task of the linguist <WSD>devising</WSD> a grammar which models the linguistic competence of the fluent native speaker is to <WSD>devise</WSD> a "finite" set of rules which are capable of specifying how to form, interpret, and pronounce an "infinite" set of well-formed sentences. 
Meaning of the word marked with <WSD> tags:  To use one's intellect to plan or design (something).