| persistent(adjective, strong, strain, flat, certain) |
| stable(adjective, calm, strong, direct, smooth) |
| firm(adjective, strain, solid, certain, determined) |
| sound(adjective, clear, reasonable, strain, sensible) |
| strong(adjective, strain, firmness, labour, hardiness) |
| unfluctuating(adjective, calm, direct, smooth, right) |
| steady(adjective, calm, strong, smooth, right) |
| invariable(adjective, change, strain, certain, ordinary) |
| constant(adjective, calm, change, strong, smooth) |
| steadfast(adjective, strong, strain, flat, firm) |
| lasting(adjective, strain, certain, fixed, firmness) |
| seamless(adjective, strain, firmness, uniform, continuous) |
| tight(adjective, strain, firmness, labour, ordered) |
| permanent(adjective, strain, usual, steady, stable) |
| durable(adjective, strain, stable, firmness, labour) |
| enduring(adjective, strong, strain, flat, firm) |
| perpetual(adjective, strain, usual, steady, stable) |
| stabile(adjective, calm, direct, smooth, right) |
| unalterable(adjective, strong, strain, flat, certain) |
| rigid(adjective, strain, fixed, firmness, even) |