To braid is to interweave or twine three or more separate strands of one or more materials in a diagonally overlapping pattern. The word is used in many contexts:

As a noun, braid refers to any object created by such weaving, particularly if it remains in a strand or rope-like configuration. Simple braids with more than three strands can be flat or tubular and generally contain an odd number of strands. Complex braids have been used to create hanging fiber artworks.

Braiding of fiber yarn creates a strand or rope that is thicker and stronger than the strands would have been separately. 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. See also Plait.

Gold braid and silver braid are components or trims of many kinds of formal dress, including military uniform (in epaulettes, aiguillettes, on headgear).

As a verb, the term refers to the process of creating a braid, either a real one, as in braiding one's hair (see French braid), or a metaphorical braiding such as He braided many different ideas into a new whole.

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.

In fiber optics and electrical and electronic cables, braid is a tubular sheath made of braided strands of metal placed around a central cable for mechanical protection or grounding purposes. Such braids are also used after flattening for bonding large components together. The numerous smaller wires comprising the braid are much more resistant to cracking under repeated motion and vibration than is a cable of larger wires.

Similar braiding is used on pressurised rubber hoses, e.g. in plumbing and hydraulic brake systems in automobiles. Braiding is also used for fibres for composite reninforcements.

Braids are also studied mathematically in braid theory, a special field of knot theory.