Descriptive of the interaction of two DNA strands, either single- or double-stranded, in which an oligonucleotide of one strand is twisted into a plait of helices, one around the other, and requires the nicking of one strand to form or dissociate such an interaction. When one of the DNA strands is circular, the structure, a ring pierced by the linear strand, is called a hemicatenane. Plectonemic is contrasted with paranemic, descriptive of an interaction between DNA strands that is formed and dissociated without the breaking of covalent bonds and therefore constitutes a weaker interaction than a plectonemic joint. Plectonemic and paranemic are often used to describe joints formed during recombination events. A related folding is toroidal, in which a plait of helices is circularised and forms a ring, or torus.