Something described as tenacious cannot easily be stopped or pulled apart; in other words, it is firm or strong. Tenacious can also describe something—such as a myth—that continues or persists for a long time, or someone who is determined to do something.

// Caleb was surprised by the crab’s tenacious grip.

// Once Linda has decided on a course of action, she can be very tenacious when it comes to seeing it through.

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"I put up a nesting box three years ago and nailed it to an oak tree. Beth and Fiona told me the next box location was ideal: seven feet up, out of view of walkways, and within three feet of the lower branches of a tenacious old fuchsia tree." — Amy Tan, The Backyard Bird Chronicles, 2024

For the more than 400 years that tenacious has been a part of the English language, it has adhered closely to its Latin antecedent: tenāx, an adjective meaning "holding fast," "clinging," or "persistent." Almost from the first, tenacious could suggest either literal adhesion or figurative stick-to-itiveness. Sandburs 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 tenāx led to the English word pertinacious, meaning "perversely persistent." You might use pertinacious for the likes of rumors and spam calls, for example.