Grassmann's law

Grassmann's law, named after its discoverer Hermann Grassmann, is a dissimilatory phonological process in Ancient Greek and Sanskrit which states that if an aspirated consonant is followed by another aspirated consonant in the next syllable, the first one loses the aspiration. The descriptive version was described for Sanskrit by Pāṇini.

Here are some examples in Greek of the effects of Grassmann's law:

In the reduplication which forms the perfect tense in both Greek and Sanskrit, if the initial consonant is aspirated, the prepended consonant is unaspirated by Grassmann's law. For instance /pʰu-ɔː/ φύω 'I grow' : /pe-pʰuː-ka/ πέφυκα 'I have grown'.

The fact that deaspiration in Greek took place after the change of Proto-Indo-European *bʰ, *dʰ, *gʰ to /pʰ, tʰ, kʰ/, and the fact that no other Indo-European languages show Grassmann's law, suggests that Grassmann's law developed separately in Greek and Sanskrit (although quite possibly due to areal influence from one language to the other), i.e. that it was not inherited from PIE. Another reason is that Grassmann's law in Greek also affects the aspirate h < s developed specifically in Greek but not in Sanskrit or most other PIE branches. (For example, *segʰō > *hekʰō > ekhō, ἔχω "I have" with dissimilation of h ... kh, but the future tense *segʰ-sō > heksō, ἕξω "I will have" was unaffected as aspiration was lost before s.) The evidence from other languages is not strictly negative: many IE branches, including Sanskrit's closest relative Iranian, merge the PIE voiced aspirated and unaspirated stops, and thus it is not possible to tell if Grassmann's law ever operated in them.

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