I didn't understand why
I do understand why
pro:sub mod v pro:rel
i didn't understand why .
aɪ WORD_BOUNDARY d ɪ d n t WORD_BOUNDARY ʌ n d ɚ s t æ n d WORD_BOUNDARY w aɪ WORD_BOUNDARY
i WORD_BOUNDARY d i d n ' t WORD_BOUNDARY u n d e r s t a n d WORD_BOUNDARY w h y WORD_BOUNDARY