| principal(adjective, important, significant, original, capital) |
| suitable(adjective, correct, right, fit, appropriate) |
| adequate(adjective, able, sufficient, enough, ample) |
| all-important(adjective, significant, essential, basic, vital) |
| appropriate(adjective, good, correct, right, reasonable) |
| bottom-line(adjective, important, significant, original, essential) |
| clause |
| compelling(adjective, significant, essential, basic, vital) |
| constituent |
| constraining(adjective, required, obligatory) |
| de rigueur(expression, adjective, idiom, significant, essential) |
| duty(noun, right, want, essential, obligation) |
| exigent(adjective, significant, essential, basic, vital) |
| given |
| inescapable(adjective, required) |
| inevitability(noun, need, essential, requirement, prerequisite) |
| involuntary(adjective, required) |
| main |
| mandate(noun, requirement) |
| necessitous(adjective, important, capital, essential, vital) |