| hard(adjective, adverb, strong, severe, strain) |
| firm(noun, adjective, close, strong, hard) |
| stiff(adjective, close, strong, hard, secure) |
| persistent(adjective, strain, firmness, labour, hardiness) |
| strong(adjective, close, hard, secure, tough) |
| stable(adjective, close, strong, hard, secure) |
| sound(adjective, good, strong, hard, secure) |
| consistent(adjective, strain, firmness, labour, ordered) |
| close(adjective, give, mean, hard, love) |
| unfluctuating(adjective, strain, firmness, labour, hardiness) |
| fast(adjective, adverb, close, strong, free) |
| stingy(adjective, close, give, mean, light) |
| niggardly(adjective, close, give, mean, poor) |
| mean(verb, adjective, close, give, poor) |
| miserly(adjective, close, give, mean, spare) |
| rigid(adjective, close, strong, secure, severe) |
| tough(adjective, strong, hard, difficult, complex) |
| parsimonious(adjective, close, give, mean, poor) |
| steady(adjective, close, strong, secure, strain) |
| arduous(adjective, hard, difficult, complex, troublesome) |