Particle verbs are combinations of a verb and particle, like eat up. They present a long-standing puzzle in syntactic theory due to the word order alternation traditionally analyzed as particle movement. Verb and particle stay together in the unmoved (continuous) word order, as in he ate up the spinach, but separate in the moved (discontinuous) order: he ate the spinach up.

Crucially, the particle can be modified in the discontinuous word order (ate the spinach right up), even by a whole phrase (ate the spinach pretty much right up), however, modification in the continuous order (*I ate right up the spinach) is ungrammatical. We also have to explain the ungrammaticality of particle modification in the continuous order (*I ate right up the spinach). While these features of particle verbs have been noted in the literature (Larsen 2014), previous analyses (Larsen 2014, Harley 1997, Ramchand 2008) either fail to predict that particle modifiers can be phrasal (totally all out of spinach) or rely on under-motivated syntactic machinery: an object movement specific to particle verbs and extra structure existing only to accommodate it.

We propose a simpler solution based on the widely adopted vP-VP shell analysis of (di)transitive verbs (Larson 1988), eliminating the need for ad-hoc functional projections. While retaining Larsen’s (2014) phrasal analysis (PrtP) to allow modification, we originate the object as an argument of the verb, not within the PrtP like Larson. Further, we integrate DegP into our PrtP for the discontinuous order only, explaining the ungrammaticality of continuous order modification. The alternation of orders is motivated by idiomaticity, where less idiomatic, decomposable constructions allow modification. This analysis accounts for the previously unnoticed interaction between phrasal modification of particles and the idiomaticity of particle-verb constructions, suggesting a condition on the syntax-semantics interface to explore in other constructions and languages.