When is my use considered an adaptation?
Whether a modification of licensed material is considered an adaptation for the purpose of CC licenses depends primarily on the applicable copyright law. Copyright law reserves to an original creator the right to create adaptations of the original work. CC licenses that allow for adaptations to be shared—all except BY-ND and BY-NC-ND—grant permission to others to create and redistribute adaptations when doing so would otherwise constitute a violation of applicable copyright law. Generally, a modification rises to the level of an adaptation under copyright law when the modified work is based on the prior work but manifests sufficient new creativity to be copyrightable, such as a translation of a novel from one language to another, or the creation of a screenplay based on a novel.
Under CC licenses, synching music in timed relation with a moving image is always considered an adaptation, whether or not it would be considered so under applicable law. Also, under version 4.0, certain uses of databases restricted by sui generis database rights also constitute adaptations (called "Adapted Material" in the 4.0 licenses), whether or not they would be considered adaptations under copyright law. For more details about adaptations in the database context, see the Data FAQ.
Note that all CC licenses allow the user to exercise the rights permitted under the license in any format or medium. Those changes are not considered adaptations even if applicable law would suggest otherwise. For example, you may redistribute a book that uses the CC BY-NC-ND license in print form when it was originally distributed online, even if you have had to make formatting changes to do so, as long as you do so in compliance with the other terms of the license.