A small region in a macromolecule from which at least four chains
emanate, and formed by reactions involving sites or groups on existing
macromolecules or by interactions between existing macromolecules.

Notes

1. The small region may be an atom, a group of atoms, or a number of
branch points connected by bonds, groups of atoms, or oligomeric chains.

2. In the majority of cases, a crosslink is a covalent structure but the term
is also used to describe sites of weaker chemical interactions, portions of
crystallites, and even physical interactions and entanglements.

A cross-link is a bond that links one polymer chain to another. They can be covalent bonds or ionic bonds. "Polymer chains" can refer to synthetic polymers or natural polymers (such as proteins). When the term "cross-linking" is used in the synthetic polymer science field, it usually refers to the use of cross-links to promote a difference in the polymers' physical properties. When "crosslinking" is used in the biological field, it refers to the use of a probe to link proteins together to check for protein–protein interactions, as well as other creative cross-linking methodologies.

Cross Link (Norwegian: Tverrsambandet) is a proposed fixed link which would connect Øygarden, northern Askøy, Meland and Radøy in Hordaland, Norway. The road is planned to give better transport within Nordhordland and from there to Askøy and Øygarden.

Specifically, the proposal includes a ferry from the Kollsnes area of Øygarden to somewhere south of Herdla in Askøy, a subsea road tunnel from the same area to Meland, and road across the island and then a new subsea section across to Radøy. Although not in any public proposals, there have been private proposals to develop Mjølkevikvarden in Askøy as a site for a new port for Bergen. This would only be possible if the Cross Link was built. Mongstad is one of several proposed locations for the new port, and the Cross Link would make it a more central location. The Cross Link would allow a small amount of traffic to bypass the main road system in central Bergen and would allow much faster transport between two large industrial sites, Kollsnes and Mongstad. A toll company has been established by the involved municipalities, although politicians from Nordhordland have stated that their top priority is to build the Nyborg Tunnel, which will reduce travel time towards Bergen, and a road package which involves upgrading part of the county road network in the area.