This thesis investigates semi-lexicality in the Dutch and Afrikaans verbal domain. The approach to semi-lexicality is an approach of grammaticalisation: semi-lexicality is the result of a grammaticalisation process. The main theoretical proposal of this thesis is that there are two stages of semi-lexicality, which have two different underlying syntactic structures. The first stage is the diachronic predecessor of the second stage. In the first stage, a semi-lexically used vocabulary item is a root Merged in the low part of the functional domain of a lexically used root. In the second stage, the root of the semi-lexically used vocabulary item is first Merged in a separate workspace with a functional head F. This complex head is then Merged in the functional domain of a lexically used root. This proposal is put to work in two case studies on semi-lexicality in the verbal domain. The first case study deals with two semi-lexically used verbs in Dutch: hoeven ‘need’ and zitten ‘sit’. In this case study, it is shown that these verbs are semi-lexical to different degrees. Furthermore, it is shown that the different degrees of semi-lexicality have a different impact on the amount of morphosyntactic variation and optionality in verb clusters containing these verbs. The second case study deals with the semi-lexical use of motion and posture verbs in Afrikaans. As in the first case study, in this case study it is shown how the degree of semi-lexicality of these verbs influences the amount of morphosyntactic variation and optionality these verbs exhibit.