‘斜线’ literally combines ‘斜’ (xié), meaning ‘slanted’ or ‘oblique’, and ‘线’ (xiàn), meaning ‘line’. Together, it refers specifically to a straight line that runs diagonally—neither horizontal nor vertical—across a surface or plane. It’s a precise geometric term commonly used in mathematics, design, cartography, and computing (e.g., for slash symbols like ‘/’).

In everyday contexts, ‘斜线’ appears when describing visual layouts—such as the diagonal stripes on a flag, the slanted roofline of a building, or the direction of a path cutting across a grid. Unlike the more general ‘线’ (line), ‘斜线’ always implies an angled orientation relative to standard axes. It’s neutral in register and appropriate in both technical and descriptive writing, though rarely used in casual speech without a clear visual or spatial reference.