In the present article the linguistic expression of MATTER will be considered with regards to (a) the prepositions involved and (b) the basic spatial meanings (BSMs) of such prepositions. The analysis will concentrate on Italian and Irish. The motivations for the choice of the preposition(s) will be sought after in the theoretical frame provided by Lakoff’s metaphorical semantics. In other words, we shall assume that the MATTER sense is a motivated extension of the spatial senses that primarily expressed by those prepositions. According to the abovementioned framework, a preposition is chosen to express MATTER when there is a metaphorically (i.e., analogically) motivated link between its BSM and the MATTER sense. A sense extension of MATTER (that is, a further sense extension of the BSMs via MATTER) shall be then examined, which – in a way consistent with another widespread metaphor – justifies the employ of MATTER to express linguistic medium.