rail

Rail is a term with multiple related meanings, primarily referring to long bars of metal used as tracks or barriers. In transportation, rails form the tracks on which trains and other wheeled vehicles run. Rails are laid in pairs along a route, supported by sleepers or ties and ballast to distribute loads and provide stability. The wheel-rail interface is central to performance, with wheel flanges helping keep vehicles on course through curves. Rails are designed to withstand repeated loading, wear, and environmental conditions.

Most modern rails are made of steel and can be jointed or continuously welded. A typical rail cross-section includes a head, web, and base. Older systems used bullhead rails; contemporary practice favors flat-bottom profiles. The standard gauge of 1,435 millimeters is widely used, though many regions employ broader or narrower gauges. Rails are fastened to sleepers or concrete ties with clips, chairs, or bolts, and ballast beneath them provides drainage and elasticity. Maintenance includes rail grinding, welding, and replacement when wear or defects become critical. High-speed and heavy-haul lines use stronger steels and larger profiles to accommodate greater speeds and loads.

Rail can also refer to a barrier or handrail used in buildings, stairs, bridges, fences, or ships. In these contexts, rails serve safety, support, and delineation. The term to rail, meaning to criticize loudly, is a separate usage and not related to the physical objects.