Lateral relations & multiple source constructions : the Old English subject relative clause and the Norwegian han mannen construction In construction grammar the term multiple inheritance has been used to talk about constructions that inherit features that can be traced back to more than one construction. The constructions involved are organized hierarchically in that the more specific construction inherits features from multiple more general and abstract constructions (Hudson 2007; Trousdale 2013). In recent years increased attention has been drawn to lateral or constructional relations which connect constructions at the same level of abstraction (Cappelle 2006; Van de Velde 2014; Traugott 2018; Diessel 2019). Adopting a nested network approach (Diessel 2019) this dissertation shows that constructions can be motivated by multiple constructions at the same level of abstraction i.e. via lateral relations. This is explored by means of two case studies. The first study investigates the change from object verb to verb object order in Old to Middle English subject relative clauses. It is argued that the principle of end weight motivated the existence of a postverbal slot which could expand under the influence of declarative main clauses. It is shown that Old English had a group of non prototypical subject relative clauses that bore formal and functional similarity to declarative main clauses. This group proves essential in the analysis of the analogical transfer of verb object order from main clauses to subject relative clauses. The second study investigates Norwegian definite noun phrases of the type han mannen (lit. ‘he man the’) in relation to three other constructions: den mannen (lit. ‘that the man the’) mannen (lit. ‘man the’) and (ha)n Per (lit. ‘he Per’). The relation of han mannen to its neighbors is considered in terms of structural similarity and contrast which is statistically evaluated with the method of partial dependence plots based on random forests. It is shown that han mannen shares relations with all three constructions individually and is partially motivated by all three. Both studies support the idea that multiple source constructions are able to motivate changes and variation of a target construction to which they are related by lateral relations i.e. they exist at the same level of abstraction.