καρδιά

Etymology: From Ancient Greek καρδία (kardia), which is the source of English medical terms like 'cardiac', 'cardiology', and 'cardiovascular'. The word shares the same Indo-European root *ḱḗr as English 'heart', Latin 'cor' (cordial), and German 'Herz'. This makes it one of the most recognizable Greek words for English speakers due to its prevalence in medical terminology. The metaphorical uses (courage, essence) parallel English 'heart' exactly, making it conceptually familiar despite the different sound.