twosided

Two-sided, sometimes written two-sided or hyphenated as two-sided, is an adjective describing something with two distinct sides or aspects. The expression is common across disciplines and everyday language. In geometry and topology, a surface is two-sided if it has two distinct faces; some surfaces, such as the sphere, are two-sided, while non-orientable surfaces like the Möbius strip are one-sided. In practical contexts, many objects have two faces: coins and playing cards have a front and back; printed materials can be produced using two-sided or duplex printing, where content appears on both sides of a sheet.

In manufacturing and materials, two-sided products include two-sided tape, which has adhesive on both faces, and two-sided materials that can be attached to two surfaces. In electronics, a two-sided printed circuit board (PCB) has conductive layers on both sides of the substrate, allowing more components in a compact area.

In economics and platform theory, a two-sided market refers to a platform that serves two distinct customer groups that provide network effects, such as buyers and sellers or advertisers and users. In media and communications, two-sided messaging or advertising addresses two audiences or passes information from both sides.

The term's usage often favors the hyphenated form two-sided in formal writing; "twosided" may appear in branding or informal contexts.