Brugmann's law

Brugmann's law, named for Karl Brugmann, is a controversial sound law stating that in the Indo-Iranian languages, an earlier Proto-Indo-European *o became *a in Proto-Indo-Iranian, but became *ā in open syllables; when it was followed by a single consonant and another vowel. For example, the Proto-Indo-European noun for 'wood' was *dόru, which in Vedic became *dāru. Everywhere else the outcome was *a, the same as the reflexes of PIE *e and *a.

The theory accounts for a number of otherwise very puzzling facts. Sanskrit has pitaras, mātaras, bhrātaras for "fathers, mothers, brothers" but svasāras for "sisters", a fact neatly explained by the traditional reconstruction of the stems as *-ter- for "father, mother, brother" but *swesor- for "sister" (cf. Latin pater, māter, frāter but soror). Similarly, the great majority of n-stem nouns in Indic have a long stem-vowel, such as brāhmāṇas "Brahmins", śvānas "dogs" (from *ḱwones), correlating with information from other Indo-European languages that these were actually on-stems. But there is one noun, ukṣan- "ox", that in the earliest Indic text, the Rigveda, shows forms like ukṣǎṇas "oxen". These were later replaced by "regular" formations (ukṣāṇas and so on, some as early as the Rigveda itself), but the notion that the short stem vowel might have been from an *en-stem is supported by the unique morphology of the Germanic forms, e.g. Old English oxa nom.singular "ox", exen plural—the Old English plural stem (e.g., the nominative) continuing Proto-Germanic *uhsiniz < *uhsenez, with e > i in noninitial syllables followed in Old English by umlaut. As in Indic, this is the only certain Old English n-stem that points to *en-vocalism rather than *on-vocalism.

Exceptions

The rule seems to only apply to an *o that is the ablaut alternant of *e. "Non-apophonic *o", that is, *o that has no alternant, develops into Indo-Iranian *ă; as in *poti- "master, lord" > Sanskrit pati-, not ˣpāti (there being no such root as ˣpet- "rule, dominate").

Several exceptions can be addressed in light of the laryngeal theory. The form traditionally reconstructed as *owis "sheep" (Sanskrit ǎvi-), is a good candidate for re-reconstructing as *h₃ewi- with an o-coloring laryngeal rather than an ablauting o-grade.

Perhaps the most convincing confirmation comes from the inflection of the perfect, wherein a Sanskrit root like sad- "sit" has sasada for "I sat" and sasāda for "he, she, it sat". The conventional 19th century wisdom saw this as some kind of "therapeutic" reaction to the Indo-Iranian falling-together of the endings *-a "I" and *-e "he/she/it" as -a, but it was troubling that the distinction was found exclusively in roots that ended with a single consonant. That is, dadarśa "saw" is both first and third person singular, even though a form like ˣdadārśa is perfectly acceptable in terms of Sanskrit syllable structure. This mystery was solved when the ending of the perfect in the first person singular was reanalyzed on the basis of Hittite evidence as *-h₂e, that is, beginning with an a-coloring laryngeal. In other words, at the time when Brugmann's Law was operative, a form of the type *se-sod-h₂e in the first person did not have an open root syllable.

A problem for this interpretation is that roots that pretty plainly must have ended in a consonant cluster including a laryngeal, such as jan- < *ǵenh₁- "beget", and which therefore should have had a short vowel throughout (like darś- "see" < *dorḱ-), nevertheless show the same patterning as sad-: jajana 1sg., jajāna 3sg. Whether this is a catastrophic failure of the theory or just leveling is a matter of taste, but after all, those who think the pattern seen in roots like sad- have a morphological, not a phonological, origin, have their own headaches, such as the total failure of this "morphological" development to include roots ending in two consonants. And such an argument would in any case cut the ground out from under the neat distributions seen in the kinship terms, the special behavior of "ox", and so on.

Perhaps the most worrisome data are adverbs like Sankrit prati, Greek pros (< *proti) (meaning "motion from or to a place or location at a place", depending on the case of the noun it governs) and some other forms, all of which appear to have ablauting vowels. They also all have a voiceless stop after the vowel, which may or may not be significant.

Current status

For all its charms, Brugmann's Law has few supporters nowadays (even Brugmann himself eventually gave up on it). Jerzy Kuryłowicz, the author of the explanation of the sasada/sasāda matter (in his Études indoeuropéennes I), eventually abandoned his analysis in favor of an appeal to the theory of marked vs unmarked morphological categories.

Modern scholars who accept Brugmann's law include Martin Joachim Kümmel, who compares it to developments in Anatolian and Tocharian and Saussure's losses of laryngeals near *o in internally reconstructing pre-PIE *o as longer than *e (Kümmel 2012:308).