The main aim of the reported study is to establish the stage of grammaticalisation of the indefinite article in Polish by contributing the results of a corpus study. We selected and analysed 20,000 sentences containing the word jeden. The obtained results demonstrate that the uses of jeden as a presentative marker and a specific marker have been both attested, which would suggest that Polish numeral has already reached the specific marker stage. Based on the statistical analysis carried out for the obtained results, a statistically significant increase in the use of jeden as an indefinite marker has been revealed. This may be interpreted as evidence for the grammaticalisation phenomena, enhanced by language contacts with article-possessing languages (English and German).