Is "two different input map to one unique target called nonlinear case " or "one unique input map to two different target called nonlinear case"? Which learning method can train these two cases or no method to train one of case?

[Ho Yeung Lee]

Is "two different input map to one unique target called nonlinear case " or "one unique input map to two different target called nonlinear case"? Which learning method can train these two cases or no method to train one of case?