Catalan, as a Romance language, finds its origins in Latin. Clearly, the evolution of Latin was not uniform everywhere, and although, in the vernacular, many of the changes that led to the birth of the Romance languages we know today followed the same pattern, there were others that made a difference: regional variations that only occurred in a specific place; a similar form in various languages; or the influences of languages predating the expansion of the Roman Empire that left their mark and contributed to the consolidation of certain innovations. That said, why do we use 'tío' in Catalan to refer to someone's father's or mother's brother, but, on the other hand, when we have to talk about a sister we use 'tía'?'Why is the masculine form of this word not accepted in Catalan? It is clear that the origin of both words is not the same. Initially, in classical Latin we found the words 'avunculus' and 'amita' which were used with a much more restricted meaning and only designated the mother's brother and the father's sister, respectively. This is because in Classical Latin a distinction was made between the maternal and paternal lines, and therefore the words 'patrols' (father's brother) and 'matertera' (mother's sister). Later, in Vulgar Latin, 'avunculus' and 'amita' They adopted the meanings we currently assign to 'uncle' and 'aunt', that is, brother and sister of someone's father or mother.