| persistent(adjective, strong, tough, continue, strain) |
| steady(adjective, calm, good, close, quiet) |
| firm(noun, adjective, calm, good, close) |
| stable(adjective, calm, good, strong, secure) |
| perpetual(adjective, sound, continue, strain, determined) |
| consistent(adjective, calm, change, strong, smooth) |
| steadfast(adjective, calm, good, close, strong) |
| permanent(adjective, calm, strong, secure, tough) |
| continual(adjective, dull, smooth, right, continue) |
| invariable(noun, adjective, calm, change, strong) |
| unfluctuating(adjective, calm, strong, secure, smooth) |
| lasting(adjective, calm, strong, secure, tough) |
| sound(adjective, calm, strong, secure, tough) |
| stiff(adjective, strain, firmness, purpose, reliable) |
| strong(adjective, calm, good, tough, strain) |
| incessant(adjective, strong, sound, continue, firm) |
| enduring(adjective, calm, close, strong, secure) |
| unchanging(adjective, calm, close, change, smooth) |
| ceaseless(adjective, dull, sound, continue, certain) |
| fast(adjective, calm, close, strong, sound) |