| key question(expression, moment, influence, reason, importance) |
| key element(expression, reason, significance, fact, factor) |
| prime cause(expression, cause, reason, value, significance) |
| prime mover(expression, cause, reason, value, significance) |
| basic premise(expression, reason, importance, significance, fact) |
| controlling factor(expression, reason, significance, factor) |
| root cause(expression, reason, significance, fact) |
| pacing item(expression, reason, importance, fact) |
| ultimate cause(expression, cause, reason, value, significance) |
| basic term(expression, reason, importance, significance, fact) |
| fundamental term(expression, reason, importance, significance, fact) |
| overriding term(expression, reason, importance, significance, fact) |
| first principle(expression, cause, value, fact) |
| crucial component(expression, reason, importance, significance, fact) |
| crucial factor(expression, moment, influence, reason, importance) |
| determinative factor(expression, moment, influence, reason, importance) |
| governing factor(expression, moment, influence, reason, importance) |
| core driver(expression, reason, significance, factor) |
| critical factor(expression, reason, significance, factor) |
| decisive factor(expression, reason, significance, factor) |