| perseverant |
| pertinacious |
| regular(adjective, dull, set, steady, stable) |
| relentless(adjective, set, strong, hard, firm) |
| smooth(adjective, even, unchanging, unbroken, undeviating) |
| solid(calm, strong, steady, fixed, even) |
| static(adjective, set, regular, fixed, even) |
| stationary(calm, strong, solid, substantial, fixed) |
| staunch(adjective, calm, strong, secure, firm) |
| straight(adjective, even, rigid, inflexible, reliable) |
| strict(hard, rigid, inflexible, obstinate, stubborn) |
| sure(calm, strong, solid, steady, even) |
| sustained(adjective, persistent, continuous, endless, relentless) |
| systematic(adjective, even, rigid, inflexible, reliable) |
| tireless |
| unadaptable(adjective, set, hard, stiff, rigid) |
| unaltered |
| unbroken(adjective, dull, steady, stable, regular) |
| undiversified(adjective, set, regular, even, constant) |
| unfading(stable, fixed, constant, enduring, lasting) |