Circular DNA refers to the type of DNA that forms a closed looped structure in bacteria, viruses, and eukaryotic organelles. There are various synonyms used for this type of DNA, depending on the context of the research and the organism under study. Some of the commonly used synonyms for circular DNA include plasmids, episomes, mitochondrial DNA, and circular chromosomes. In addition, circular DNA may be referred to as supercoiled DNA or relaxed DNA, indicating the level of tension in the double helix. These different terminologies are used to specify the characteristics and function of circular DNA, which is crucial in many areas of molecular biology, genetics, and biotechnology.