Changing the verb from ending in -다 to -이다 makes the verb to take the causative form. 멍들다 = to get bruised. 멍들"이"다 = to "make" s.o get bruised = to bruise (s.o) (i.e. to inflict bruise on s.o) 울다 = to cry (너가) 울어도 = even if you cry 울"리"다 = to "make" s.o cry (너가) (나를) 울려도 = even if you make me cry As such, the verbs are in different form and procure different meanings. Verbs in causative form: (내가) 때로는 모진 말로 (너를) 멍들이며 울려도: Even if (I) bruise (you) and make (you) cry with harsh words Verbs in non-causative form: (내가) 때로는 모진 말로 멍들며 울어도: Even if (I) get bruised and cry from harsh words