In the context of EU-funded projects, a "sister project" refers to a complementary initiative that is financed under the same or a related EU funding program. These projects often share similar objectives, target groups, or thematic areas, and are designed to mutually enrich each other by exchanging insights, methodologies, and results to enhance their impact and reach within the European Union. Sister projects collaborate to leverage synergies, avoid duplication of efforts, and maximize the efficient use of resources towards achieving their common goals.