'''Brugmann's law''', named for Karl_Brugmann, states that Proto-Indo-European ''{{PIE|*o}}'' changed into Proto-Indo-Iranian ''*a'' in Closed_syllables (syllables ending in a Consonant), but into ''*ā'' in Open_syllables (syllables ending in a Vowel). The law has reasonable but not universal acceptance. Some consider it a morphological rule rather than a proper Sound_law that allowed to preserve Ablaut patterns at the time of the Proto-Indo-Iranian merger of PIE ''{{PIE|*e, *o, *a}}'' into ''*a''. {{ling-stub}} Category:Sound_laws Category:Eponymous_laws Category:Indo-European_linguistics