| resolute(adjective, strong, tough, keen, flat) |
| steadfast(adjective, strong, tough, flat, firm) |
| persistent(adjective, quiet, understanding, strong, tough) |
| dogged(adjective, strong, tough, firm, ready) |
| determined(adjective, strong, tough, keen, flat) |
| indefatigable(adjective, strong, firm, difficult, determined) |
| tireless(adjective, strong, firm, difficult, energetic) |
| diligent(adjective, keen, difficult, intense, energetic) |
| tenacious(adjective, strong, tough, flat, firm) |
| steady(adjective, strong, flat, firm, determined) |
| stubborn(adjective, characteristic, quality, strong, tough) |
| unflagging(adjective, strong, firm, difficult, energetic) |
| assiduous(adjective, keen, difficult, intense, energetic) |
| unwavering(adjective, strong, flat, firm, certain) |
| constant(adjective, strong, flat, firm, certain) |
| firm(adjective, strong, tough, certain, determined) |
| unfaltering(adjective, strong, firm, determined, steady) |
| obstinate(adjective, strong, tough, firm, determined) |
| enduring(verb, adjective, quiet, set, strong) |
| persisting(verb, adjective, continuing, abiding, resolving) |