| decisive(adjective, definite, precise, sure, final) |
| determining factor(noun, expression, idiom) |
| incentive(noun, feeling, cause, reason, object) |
| ingredient(noun, feature, influence, issue, element) |
| portion(feature, influence, issue, element) |
| antigenic determinant |
| conclusive(adjective, definite, final) |
| end(noun, cause, reason, object, element) |
| epitope |
| influence(noun, feature, cause, point, reason) |
| inspiration(noun, cause, influence, reason, object) |
| motivator(noun, cause, incentive, motive, instigator) |
| origin(noun, cause, reason, base, matter) |
| origination(noun, cause, source, foundation, basis) |
| root(noun, cause, reason, object, base) |
| agency(noun, feature, influence, point, reason) |
| authority(cause, foundation, basis) |
| birth(cause, source, derivation) |
| call(noun, cause, reason, base, element) |
| catalyst(noun, reason, spur, lure, stimulus) |