per ‧ ti ‧ na ‧ cious /ˌpɜːtəˈneɪʃəs◂, ˌpɜːtɪˈneɪʃəs◂ $ ˌpɜːr-/ BrE AmE adjective formal
[ Date: 1600-1700 ; Language: Latin ; Origin: pertinax , from tenax ; ⇨ ↑ tenacious ]
continuing to believe something or to do something in a very determined way SYN tenacious
—pertinaciously adverb
—pertinacity /-ˈnæsəti, -ˈnæsɪti/ noun [uncountable]