This study compares and contrasts the form and function of the spatio-temporal expressions formed with the noun ḥꜢ-t “front’ — m_ḥꜢt, r_ḥꜢt and ẖr_ḥꜢt — in order to see firstly if they change in usage over time and secondly to seek out the basis of any change. Concerning the first question, a diachronic analysis of the distinct usage patterns of m_ḥꜢt, r_ḥꜢt and ẖr_ḥꜢt calls into question the extent to which we can unequivocally categorise these forms as compound prepositions and adverbs. Some of the ḥꜢt forms that establish spatial relations with fronted Grounds could instead be classified as prepositional phrases comprising the relational noun ḥꜢ-t “front’ plus the simple prepositions m, r and ẖr. Nevertheless, from the Old Kingdom on, clear syntactic evidence exists for the use of these forms in more grammaticalised constructions as compound prepositions and adverbs. On the basis of this data, linguistic hypotheses about the developmental patterns of compound prepositions and adverbs (particularly Hopper & Traugott 1993) are tested. Changing function is then interrogated from cognitive and pragmatic perspectives, in order to interrogate the theory prevalent in linguistics and cognitive sciences that the description of time is based metaphorically on the description of space and that abstract meaning extends from temporal relations (Heine, Claudi & Hünnemeyer 1991). Although the ḥꜢt compounds establish a wide range of abstract relations during the late New Kingdom, abstractness is evident in particular constructions from amongst the earliest attestations of some of these forms. Semantic networks based on the uses of these forms are thus proposed and the role of metaphor in semantic change is evaluated.