tenacious

For all of its nearly 400 years, "tenacious" has adhered closely to its Latin antecedent: tenax, an adjective meaning "tending to hold fast." Almost from the first, "tenacious" could suggest either literal adhesion or figurative stick-to-itiveness. Sticker burrs are tenacious, and so are athletes who don't let defeat get them down. We use "tenacious" of a good memory, too - one that has a better than average capacity to hold information. But you can also have too much of a good thing. The addition in Latin of the prefix per- ("thoroughly") to "tenax" led to the English word pertinacious, meaning "perversely persistent." You might use "pertinacious" for the likes of rumors and telemarketers, for example.