A braid (also called plait) is a complex structure or pattern formed by intertwining three or more strands of flexible material such as textile fibers, wire, or human hair. Compared to the process of weaving a wide sheet of cloth from two separate, perpendicular groups of strands (warp and weft), a braid is usually long and narrow, with each component strand functionally equivalent in zigzagging forward through the overlapping mass of the others.
The simplest possible braid is a flat, solid three-strand structure. More complex braids can be constructed from an arbitrary (but usually odd) number of strands to create a wider range of structures: wider ribbon-like bands, hollow or solid cylindrical cords, or broad mats which resemble a rudimentary perpendicular weave.
Braiding creates a composite rope that is thicker and stronger than the non-interlaced strands of yarn. Braided ropes are preferred by arborists and rock climbers because they do not twist under load, as does an ordinary twisted-strand rope. These ropes consist of one or more concentric tubular braided jackets surrounding a single untwisted yarn of straight fibers.
In electrical and electronic cables, braid is a tubular sheath made of braided strands of metal placed around a central cable for shielding against electromagnetic interference. The braid is grounded while the central conductor(s) carry the signal.
Flat braids made of many copper wires are also sometimes used for flexible electrical connections between large components. The numerous smaller wires comprising the braid are much more resistant to breaking under repeated motion and vibration than is a cable of larger wires.
Braids are often used figuratively to represent interweaving or combination, such as in "He braided many different ideas into a new whole."
Braiding happens when a river is carrying vast amounts of eroded sediment. Sediment is deposited as islands in the channel causing the river to split up into many winding channels.
In some river and stream systems, small streams join together and redivide in many places. Such stream systems are said to be braided. These are often found in alluvial fans at the outlet of canyons. This is a result of heavy sediment deposition at high flows followed by re-erosion at low flows. See also river delta.