Drummond's Law (named after the fictional linguist Colin Drummond) is a sound change in the northern group of Hesperic. In North Hesperic, consonants followed by Proto-Hesperic *x were velarized, with the *x itself disappearing. Stops became velar stops, preserving their laryngeal features (e.g., *t'x > *k'); *sx became *h, and *nx became the velar nasal *ng. The reflexes of liquids under Drummond's Law vary by branch:
- In Albic, they became *ɣ and later *g.
- In Hercynian, they became *ɣ, conventionally transcribed *gh.
- In Alpianic, they became sounds transcribed *ĺ (probably [ɫ]) and *ŕ (probably [ʀ]).
The semivowels apparently did not change.
The South Hesperic languages did not undergo this change.