| firm(adjective, hard, usual, regular) |
| inflexible(adjective, hard, severe, harsh) |
| rigid(adjective, hard, severe, cruel) |
| unalterable(adjective, hard, fixed, stiff) |
| invariable(adjective, hard, stiff, inflexible) |
| stiff(adjective, hard, severe, harsh) |
| certain(adjective, determined, usual, regular) |
| strict(adjective, hard, severe, harsh) |
| fixed(adjective, hard, firm, determined) |
| immovable(adjective, hard, cruel, usual) |
| incontestable(adjective, certain, unquestionable, indisputable) |
| obstinate(adjective, hard, cruel, determined) |
| sure(adjective, certain, fixed, rigid) |
| unassailable(adjective, certain, unquestionable, indisputable) |
| accurate(certain, unquestionable, indisputable, unassailable) |
| apodictic(certain, unquestionable, indisputable, unassailable) |
| beyond question(expression, certain, unquestionable, indisputable) |
| can bet on it(expression, certain, unquestionable, indisputable) |
| determined(adjective, hard, firm, usual) |
| double-checked(certain, unquestionable, indisputable, unassailable) |