Brugmann's law, named for Karl Brugmann, is a sound law stating that in the Indo-Iranian languages, the earlier Proto-Indo-European normally became in Proto-Indo-Iranian but in open syllables if it was followed by one consonant and another vowel. For example, the Proto-Indo-European noun for 'wood' was , which in Vedic became . Everywhere else, the outcome was , the same as the reflexes of PIE and . Overview The theory accounts for a number of otherwise puzzling facts. Sanskrit has for "fathers, mothers, brothers" but for "sisters", a fact neatly explained by the traditional reconstruction of the stems as for "father, mother, brother" but for "sister" (cf. Latin but ). Similarly, the vast majority of n-stem nouns in Indic have a long stem-vowel, such as "Brahmins", "dogs" (from ), correlating with information from other Indo-European languages that they were originally *on-stems. There are also some exceptions, including "ox", which in the earliest Indic text, the Rigveda, shows forms as "oxen". They were later replaced by "regular" formations ( and so on, some as early as the Rigveda itself), but the notion that the short stem vowel might have been from an -stem is supported by the unique morphology of the Germanic forms: Old English nominative singular "ox", plural; the Old English plural stem, such as the nominative, continues Proto-Germanic < , with e > i in noninitial syllables followed, in Old English, by an umlaut. This is the only Old English n-stem that certainly points to -vocalism, rather than -vocalism. Exceptions The rule seems to apply to only an that is the ablaut alternant of . Non-apophonic , with no alternant, developed into Indo-Iranian : "master, lord" > Sanskrit , not (there is no such root as "rule, dominate"). Alternatively, it is explained by the voiceless consonant after the vowel (see also Sanskrit < ), but to adopt a form of the sound law that affects only in open syllables, followed by a voiced consonant, seems to be a slim basis for a rule that is so general in Indo-Iranian. Limiting the original environment to that before voiceless consonants then requires levelling of long-vowel forms to perfects and nouns with final voiceless consonants in Pre-Indo-Iranian. That faces particular problems in explaining the archaic form 'he/she has reached' < , with its very idiosyncratic synchronic relation to Sanskrit 'reach'. Several exceptions can be addressed by the laryngeal theory. The form that is