| persistent(adjective, strong, tough, continue, strain) |
| stable(adjective, strong, secure, tough, strain) |
| lasting(adjective, calm, strong, secure, tough) |
| everlasting(adjective, strong, steady, stable, fixed) |
| firm(adjective, calm, strong, secure, tough) |
| enduring(adjective, calm, strong, secure, tough) |
| constant(adjective, calm, strong, secure, tough) |
| perpetual(adjective, strain, usual, steady, stable) |
| strong(adjective, strain, firmness, labour, hardiness) |
| durable(adjective, time, continue, strain, stable) |
| sound(adjective, strain, firmness, labour, hardiness) |
| consistent(adjective, strain, usual, steady, stable) |
| eternal(adjective, pause, steady, fixed, persistent) |
| unfluctuating(adjective, calm, strong, secure, strain) |
| fixed(verb, adjective, strong, secure, tough) |
| stiff(adjective, strain, firmness, labour, hardiness) |
| invariable(adjective, calm, strong, secure, strain) |
| steadfast(adjective, calm, strong, secure, strain) |
| unalterable(adjective, calm, strong, secure, strain) |
| stationary(adjective, moving, strain, fixed, firmness) |