The PMC Open Access Subset includes millions of journal articles and preprints that are made available under license terms that allow reuse. Not all articles in PMC are available for text mining or other reuse; many are under copyright. Articles in the PMC Open Access Subset are made available under Creative Commons or similar licenses that allow more liberal redistribution and reuse than a traditionally copyrighted work. The PMC Open Access Subset is one part of the PMC Article Datasets.