Structural steelwork

The twenty-third entry is a contraflecha, and the English word waiting for it is camber — a noun lent to four trades and owned by none of them. For the road builder, the camber is the fall from the crown of a carriageway down to the gutter, put there so that rain leaves the surface. For the aerodynamicist, the camber of a wing is the curvature of the line drawn midway between the upper and lower surfaces, and it is what makes the wing lift. In a garage, camber is the angle at which a wheel leans in or out from the vertical, and a mechanic who says the camber is out means the car pulls to one side. And in a steel shop it is this entry: the beam is made with a rise built into it, so that it sits flat once the weight is on. One noun, four trades, four different tools for measuring it. Nothing in the word itself says which is meant, so a reader meeting camber cold has to be told by the trade standing around it.