| dominant factor(expression, reason, importance, significance) |
| driving factor(expression, reason, importance, significance) |
| emergency(noun, trouble, difficulty, climax, crisis) |
| first principle(expression, reason, importance, significance) |
| fundamental cause(expression, reason, importance, significance) |
| fundamental premise(expression, reason, importance, significance) |
| fundamental principle(expression, reason, importance, significance) |
| fundamental reason(expression, reason, importance, significance) |
| fundamental term(expression, reason, importance, significance) |
| initial cause(expression, reason, importance, significance) |
| issue main reason(expression, reason, importance, significance) |
| key condition(expression, reason, importance, significance) |
| key element(expression, reason, importance, significance) |
| key enabler(expression, reason, importance, significance) |
| key factor(expression, moment, influence, importance) |
| key idea(expression, reason, importance, significance) |
| key pillar(expression, reason, importance, significance) |
| key reason(expression, reason, importance, significance) |
| main cause(expression, reason, importance, significance) |
| main condition(expression, reason, importance, significance) |