The phrase 'under copyright' means that a particular work has granted its author exclusive rights to reproduce, distribute, and display the work. Some synonyms for 'under copyright' include 'copyrighted,' 'proprietary,' 'intellectual property,' 'registered trademark,' and 'patented.' These synonyms are commonly used to describe works such as books, music, movies, or software that are legally owned and controlled by the creators. It is important to acknowledge and respect works that are under copyright as unauthorized use or reproduction can result in legal consequences. Thus, using synonyms indicating copyrighted materials can serve as a clear indication to others, that the work is owned and protected.