| persistent(adjective, strong, strain, flat, certain) |
| firm(adjective, calm, strong, hard, secure) |
| stable(adjective, strong, secure, strain, flat) |
| hard(adjective, strain, firmness, labour, hardiness) |
| stiff(adjective, strain, firmness, labour, hardiness) |
| consistent(adjective, strong, strain, flat, certain) |
| unfluctuating(adjective, calm, strong, secure, strain) |
| strong(adjective, strain, firmness, labour, hardiness) |
| sound(adjective, strain, firmness, labour, hardiness) |
| invariable(adjective, calm, strong, secure, strain) |
| permanent(adjective, calm, strong, secure, strain) |
| constant(adjective, calm, strong, secure, strain) |
| rigid(adjective, severe, strain, harsh, cruel) |
| settled(adjective, strain, firmness, established, labour) |
| steadfast(adjective, calm, strong, secure, strain) |
| unchangeable(adjective, calm, strong, definite, fixed) |
| unyielding(adjective, strain, firmness, labour, hardiness) |
| fixed(adjective, strong, hard, secure, severe) |
| lasting(adjective, calm, strong, secure, strain) |
| enduring(adjective, calm, strong, secure, strain) |