| quick(adjective, adverb, activity, direct, express) |
| rapid(adjective, adverb, direct, keen, express) |
| speedy(adjective, adverb, direct, keen, express) |
| swift(verb, adjective, adverb, activity, open) |
| firm(noun, adjective, adverb, calm, close) |
| persistent(adjective, strong, tough, strain, firm) |
| stable(adjective, adverb, strong, secure, tough) |
| strong(adjective, calm, secure, tough, continue) |
| sound(adjective, characteristic, calm, strong, secure) |
| expeditious(adjective, adverb, activity, prompt, quick) |
| steadfast(adjective, characteristic, calm, close, strong) |
| lasting(adjective, state, strain, firmness, labour) |
| unfluctuating(adjective, calm, strong, secure, strain) |
| hard(adjective, adverb, strain, firm, intense) |
| stiff(adjective, great, secure, strain, firm) |
| tight(adjective, adverb, close, strong, free) |
| permanent(adjective, state, strain, firmness, labour) |
| enduring(adjective, state, calm, close, strong) |
| durable(adjective, calm, strong, secure, tough) |
| substantial(adjective, calm, strong, secure, tough) |