Trade dress, protected under Lanham Act § 43(a), covers the overall look and feel of a product or its packaging, such as shape, color scheme, texture, and layout, when consumers associate that appearance with a particular source rather than treating it as purely decorative or functional.

Protection requires two things: nonfunctionality, meaning the design is not essential to the product's use or does not affect its cost or quality, and distinctiveness, either inherent or acquired through secondary meaning. Following Two Pesos v. Taco Cabana and Wal-Mart Stores v. Samara Brothers, packaging trade dress can sometimes be inherently distinctive, but product design trade dress can never be inherently distinctive and always requires proof of acquired secondary meaning.

In a simulation, the functional-versus-ornamental classification acts as a binary gate: if a design feature is found functional, the trade dress branch is unavailable entirely, regardless of how distinctive or well-recognized the design has become.

Companies assert trade dress claims to stop knockoffs that copy a product's overall look and feel even when the competitor avoids copying any word mark or logo outright. Defendants primarily attack functionality, arguing the design serves a genuine utilitarian purpose, and lack of secondary meaning, arguing consumers do not actually associate the appearance with a single source.