Tenacious means holding on and refusing to let go, whatever comes. A tenacious campaigner, a tenacious grip, a tenacious cough that lasted three weeks.
Applied to people it is a compliment about persistence rather than about ability, and it is used most of somebody fighting a long battle they might lose. Applied to things it is literal: tenacious mud, a tenacious stain. The noun is tenacity, which is commoner than the adjective in writing about business and sport. Compare stubborn, which is the same quality described by somebody who wishes you would stop, and dogged, which is nearly identical and slightly warmer.
1adjectivetenaciousRefusing to give up, however hard it gets.
“She was tenacious about it for eleven years.”
synonyms: persistent, dogged, determined
2adjectiveholdingHolding on tightly and hard to remove.
“Ivy has a tenacious grip on old brickwork.”
tenacious is a quality of holding on.
Also accepted in games: persistent
Latin tenax meant holding fast, from tenere, to hold — the same verb behind tenant, tenure, contain and, at a remove, tenor. Tenacity is grip, and the word has never let go of that picture.
Proto-Indo-European
*ten-
Latin
tenāx — holding fast, clinging
English, today
tenacious
Built from
From Latin tenāx (“holding fast, clinging”), from teneo (“to hold”), ious.
Etymology from Wiktionary, CC BY-SA