A collection is an aggregation or grouping of individual works that have been assembled together without altering their content. In a collection, each work remains intact and continues to be governed by its original CC license. The act of compiling the works into one package (like a book, website, or exhibition) does not create a new, modified work.
License Compatibility:
Additional Content and Overall Collection Licensing:
2007 USA stamp by Daniel R. Blume. CC BY-SA 2.0
Moldova Stamps by Bill Smith. CC BY 2.0
Paraguay postage stamp - Philodendron robustum by Stamp Boy CC BY-SA 2.0
Post of Uzbekistan, Public domain, via Wikimedia Commons
Post of Romania, Public domain, via Wikimedia Commons
The gallery above is an example of a slide-show collection of CC-licensed and public domain images. Each image retains its own individual CC license (or public domain attribution) while the collection as a whole contains a different license. As the creator of this collection, I am only licensing the compilation, not the individual images.
"Stamp Collection" by Lori Looney. CC BY 4.0