Pertinacious /(?)/

Per·ti·na·cious

Pertinacious

a.
  1. Holding or adhering to any opinion, purpose, or design, with obstinacy; perversely persistent; obstinate; as, pertinacious plotters; a pertinacious beggar.
  2. Resolute; persevering; constant; steady.
    Diligence is a steady, constant, and pertinacious study.