Remove the first syllable of pertinacious and say what remains out loud: you’ll hear something that sounds a lot like the word tenacious, meaning “tending to adhere or cling.” The similarity between pertinacious and tenacious isn’t mere coincidence; both words derive from tenax, the Latin word for “tenacious,” and ultimately from the verb tenēre, meaning “to hold.” Another descendant of tenēre is tenure, a word that is typically used of the right to hold a job (especially a teaching position) for as long as desired.