Secondary imperfectivisation is reverbalisation.

We argue that secondary imperfectivisation in Serbo-Croatian (and possibly in Slavic more generally) is a procedure whereby a new verb is derived from a perfective verb, i.e., the perfective verb gets reverbalised. This operation takes a perfective verb, that is, a verbal structure including an aspectual projection that restricts its interpretation aspectually (but also adds some lexical semantic content) and turns it into a bare P. The new verb preserves the conceptually enriched semantics, but not the structurally derived aspectual restriction, which gets overwritten by the newly projected category. The inner aspect of the verb is thus reset to the unvalued, i.e., aspectually unrestricted default. The verb gets interpreted as imperfective by scalar implicature: had the speaker intended the perfective interpretation, they would have used the more specific and computationally cheaper expression involving the perfective verb. On the morphophonological side, assuming with a host of literature that the verbal category is realised by theme vowels (Spyropoulos et al., 2015 and Panagiotidis et al., 2017 for Greek, Svenonius, 2004a for Russian, Jabłońska, 2004, 2007 for Polish, Biskup, 2019 for Czech, Milosavljević & Arsenijević, 2022 for Serbo-Croatian), imperfectivisation amounts to stacking theme vowels. Support for the view comes from Simonović et al. (2023), who arrive at the same conclusion on morphophonological grounds.