| sound(adjective, reasonable, strain, sensible, rational) |
| stable(adjective, strain, firmness, labour, hardiness) |
| strong(adjective, strain, firmness, labour, hardiness) |
| consistent(adjective, sound, strain, sensible, rational) |
| firm(adjective, strain, firmness, labour, hardiness) |
| stiff(adjective, strain, firmness, labour, hardiness) |
| viable(adjective, strain, firmness, labour, hardiness) |
| impregnable(adjective, strain, firmness, labour, safety) |
| durable(adjective, strain, firmness, labour, hardiness) |
| fast(adjective, strain, firmness, labour, hardiness) |
| refractory(adjective, strain, firmness, labour, hardiness) |
| resilient(adjective, strain, firmness, labour, hardiness) |
| rock-solid(adjective, strain, firmness, labour, hardiness) |
| stout(adjective, strain, firmness, labour, hardiness) |
| substantial(adjective, strain, firmness, labour, hardiness) |
| tolerant(adjective, sound, strain, sensible, rational) |
| justifiable(adjective, sound, right, reasonable, slight) |
| defensible(adjective, attack, sound, right, reasonable) |
| plausible(adjective, sound, reasonable, slight, sensible) |
| credible(adjective, sound, reasonable, sensible, rational) |