| necessary(adjective, sound, right, essential, obligation) |
| mandatory(adjective, right, significant, affected, essential) |
| compulsory(adjective, sound, important, certain, true) |
| requisite(adjective, appropriate, proper, significant, suitable) |
| essential(adjective, important, significant, critical, basic) |
| imperative(adjective, important, significant, essential, basic) |
| required(adjective, right, significant, essential, basic) |
| binding(adjective, sound, certain, true, significant) |
| indispensable(adjective, important, significant, essential, critical) |
| prerequisite(adjective, significant, essential, basic, vital) |
| inevitable(adjective, certain, obvious, expected, predictable) |
| peremptory(adjective, affected, duty, compulsion, strained) |
| involuntary(adjective, affected, strained, unwilling, unnatural) |
| demanded |
| incumbent |
| bounden(adjective, necessary, required, conclusive, obliged) |
| constraining(adjective, required) |
| de rigueur(expression, adjective, right, significant, essential) |
| forced(adjective, affected, strained, artificial, unwilling) |
| must(adjective, required) |