울다(ul-da, ulda)
The act of expressing emotions by making sounds or shedding tears
When to use
Expressing emotions, Human subject, May include sound or sobbing
The nuance
‘울다’ primarily means expressing strong emotions by making sounds or shedding tears, used only with human subjects.
눈물나다(nun-mul-na-da, nunmulnada)
The physical phenomenon of tears coming out of the eyes
When to use
Tears occurrence, Human/animal/situation subject, May be unrelated to emotion
The nuance
‘눈물나다’ describes the state of tears flowing from the eyes and can be used for humans, animals, or situations.