conviction [convictions](firmly held belief) noun [UK: kən.ˈvɪk.ʃn̩] [US: kən.ˈvɪk.ʃn̩]He has very firm convictions. = Tiene unas convicciones muy firmes.
firme convicciónadjective
pertinacious(holding tenaciously to an opinion or purpose) adjective [UK: ˌpɜː.tɪ.ˈneɪ.ʃəs] [US: ˌpɝː.tɪ.ˈneɪ.ʃəs]