per·sist 
(pər-sĭst)
(pər-sĭst)intr.v. per·sist·ed, per·sist·ing, per·sists
1. To be obstinately repetitious, insistent, or tenacious.
2. To hold firmly and steadfastly to a purpose, state, or undertaking despite obstacles, warnings, or setbacks.
3. To continue in existence; last: hostilities that have persisted for years.
[Latin persistere : per-, per- + sistere, to stand; see stā- in the Appendix of Indo-European roots.]
per·sister n.