Abstract Beck et al. (2009) and much follow-up research (including Bochnak 2015; Bowler 2016; Deal and Hohaus 2019) argue that languages systematically differ in the semantics of gradable predicates like tall and old , with some languages adopting a vague, delineation-based semantics and others adopting a relational, degree-based semantics. Beck et al. (2009) capture this point of variation in the so-called Degree Semantics Parameter. Based on elicitation and corpus data, we suggest here that the grammar of Samoan (Austronesian, Oceanic; Independent State of Samoa, American Samoa) has recently undergone a change from one parameter setting to the other, triggered by the addition of a degree-based comparative operator to the functional lexicon of the language. This operator developed through lexical and syntactic re-analysis from a directional particle. In Samoan, the grammar of degree is thus modelled after the grammar of another scalar domain, directed motion in space, a strategy that the typological literature suggests is cross-linguistically common.