det er mandag.

The phrase 'det er mandag' directly translates to 'it is Monday' in English. Let's break down the etymology of each word: * **det**: This is the neuter singular definite article and demonstrative pronoun in Danish, meaning 'it' or 'the'. It originates from Old Norse 'þat', which itself comes from Proto-Germanic '*þat*' (meaning 'that'). This word has cognates in other Germanic languages, such as English 'that', German 'das', and Swedish 'det'. * **er**: This is the present tense form of the verb 'at være' (to be). It comes from Old Norse 'era' or 'es', ultimately from Proto-Germanic '*iz*' or '*es-' (meaning 'is'). This verb is a core part of Indo-European languages, with cognates in English 'is', German 'ist', Latin 'est', and Greek 'esti'. * **mandag**: This word means 'Monday'. It derives from Old Norse 'mánadagr', which literally means 'moon day'. This pattern is common across many Germanic languages, reflecting the ancient practice of naming days of the week after celestial bodies and Norse gods. * 'måne' (moon) comes from Old Norse 'máni', from Proto-Germanic '*mēnô'. * 'dag' (day) comes from Old Norse 'dagr', from Proto-Germanic '*dagaz'. Compare with English 'Monday' (from Old English 'Mōnandæg', 'moon's day'), German 'Montag', and Dutch 'maandag', all sharing this lunar origin.