横 (héng) as an adjective means 'horizontal, crosswise' — it describes the physical orientation of a line or object, opposite of 竖 (shù 'vertical'). Unlike 横向 (héng xiàng), which is used for abstract, lateral relationships (e.g., cross-departmental), 横 is concrete and spatial. 水平 (shuǐ píng) is a noun meaning 'level' (of skill/standard), not a synonym for orientation.