EN
The interest of the author is in the tangled fates of two synonymous, and partially univocal words in the title: powinność ‘duty’ and obowiązek ‘obligation’. The author follows the two words’ quantitatively and semantically different, but always interwoven presence in the history of the Polish language, using dictionary data and, for contemporary times, data from the National Corpus of Polish. After an initial predominance of powinność, from the 18th century on, obowiązek takes the lead quantitatively, while powinność gradually becomes more clearly linked with the meaning of ‘serious internal moral obligation’ and formal language, leaving to obowiązek mainly the field of legal and administrative duties, and thereby the official style. Nonetheless, a complete semantic and stylistic separation of these two synonymous words has not as yet happened.