Proto-Indo-European sound law
Bartholomae's law, sometimes referred to as the Buddha rule,[1] is a Proto-Indo-European sound law affecting consonant clusters, most clearly in the Indo-Iranian languages. It states that in a cluster of two or more obstruents (stops or the sibilant *s), any one of which is a voiced aspirated stop anywhere in the sequence, the whole cluster becomes voiced and aspirated. Thus, to the Proto-Indo-European root *bʰewdʰ- 'learn, become aware of', the participle *bʰudʰ-to- 'enlightened' loses the aspiration of the first stop (following Grassmann's law) and with the application of Bartholomae's law and regular vowel changes gives Sanskrit buddha 'enlightened'. The law is named after German linguist Christian Bartholomae, who first described it in 1883.