Idioms, collocations, and structure

Phrasal idioms have been used as evidence in syntactic theorizing for decades. A common assumption, occasionally made explicit (e.g., Larson 2017), is that non-literal phrasal idioms differ significantly from completely literal collocations in the kinds of syntactic structures they can be built from. I show with a detailed empirical study that this is false. In fact, the syntactic constraints on idioms and collocations are identical. In particular, patterns that are missing from one are missing from the other, most strikingly ditransitives with a fixed first object and open second object (*throw the wolves X). Idioms and collocations should therefore be treated the same, as a broad class of conventionalized expressions. I propose a new analysis of the syntactic forms that conventionalized expressions can take. Unlike most previous analyses, I take the open slots to be part of the expression, and the task then becomes to explain the distribution of the open slots. A structural constraint on open slots accounts for the missing ditransitive pattern. It also explains why expressions with a fixed subject but open object are rare, but also why certain examples of this pattern do exist in English and in other languages.