| abiding(adjective, strong, tough, continue, flat) |
| inveterate(adjective, usual, obstinate, established, insistent) |
| perennial(adjective, continue, constant, continuous, enduring) |
| persisting(adjective, strong, tough, firm, determined) |
| recurrent(adjective, steady, regular, constant, continuous) |
| regular(adjective, usual, steady, routine, normal) |
| single-minded(adjective, tough, intense, deliberate, determined) |
| unchangeable(adjective, strong, certain, definite, resolute) |
| devoted(adjective, strong, firm, determined, steady) |
| immutable(adjective, strong, firm, stable, constant) |
| set(adjective, strong, tough, flat, firm) |
| unchanging(adjective, firm, certain, steady, stable) |
| assiduous(adjective, determined) |
| faithful(adjective, strong, firm, certain, steady) |
| frequent(adjective, common, steady, regular, constant) |
| indomitable(adjective, strong, firm, determined, steady) |
| industrious(adjective, perseverance, hardworking) |
| sedulous |
| tough(adjective, firm, unreasonable, grim, resolute) |
| undeviating(adjective, strong, flat, intense, certain) |