Grassmann's Law

Grassmann's Law describes a process of aspirate dissimilation that operated independently in both Ancient Greek and Sanskrit. When a root contained two aspirated consonants, the first one lost its aspiration. The law was formulated by Hermann Grassmann in 1862. In Greek, the PIE root *bʰewdʰ- 'to be aware' shows the expected initial aspiration in its basic form πεύθομαι (peuthomai), where *bʰ has lost aspiration to *p because of the following aspirate *dʰ (reflected as θ). However, when a suffix removes the second aspirate, the first one resurfaces: cf. the reduplicated form πέ-πυσ-μαι (pe-pus-mai), where the aspiration has been lost from the second consonant by other processes, and the root-initial consonant remains unaspirated because the dissimilation had already taken place at an earlier stage. In Sanskrit, the same root *bʰewdʰ- appears as bodh- with the first aspirate intact, because here it is the second aspirate that was retained. The classic example is the reduplication pattern: the root dhā- 'to place' reduplicates as da-dhā-ti (not **dha-dhā-ti), with the first aspirate losing its aspiration. Grassmann's Law is notable for having operated independently in two branches that had already separated. This parallel development suggests that the motivation — avoiding sequences of two aspirated consonants — was a natural phonological tendency rather than an inherited feature. The law predates Grimm's Law in Germanic, which is why its effects are not visible there: PIE aspirates had already become plain voiced stops before any dissimilation could apply. The discovery of Grassmann's Law was historically significant because it helped explain apparent irregularities in the Greek and Sanskrit consonant systems and demonstrated that sound changes could be precisely formulated as rules.