| exaction(concern, demand, need, essential, requirement) |
| exception(noun, condition) |
| exemption(noun, condition) |
| exigency(concern, demand, need, essential, requirement) |
| fine print(noun, expression, condition, essential, requirement) |
| fundamental(noun, concern, demand, need, essential) |
| godsend(need, essential, requirement, prerequisite, essentiality) |
| imperative(noun, concern, demand, need, essential) |
| indispensability(need, essential, requirement, prerequisite, essentiality) |
| inevitability(need, essential, requirement, prerequisite, essentiality) |
| inexorableness(need, essential, requirement, prerequisite, essentiality) |
| life or death(expression, idiom, need, essential, requirement) |
| modification(noun, condition) |
| necessary(need, essential, obligation, requirement, necessity) |
| needfulness(need, essential, requirement, prerequisite, essentiality) |
| no alternative(expression, need, essential, requirement, prerequisite) |
| no choice(expression, need, essential, requirement, prerequisite) |
| obligation(condition, need, essential, requirement, necessity) |
| pinch(concern, demand, need, essential, requirement) |
| preconditions |