What is the critical legal distinction between 'Fair Use' and trademark infringement when incorporating competitor names into product descriptions?

The critical legal distinction between 'Fair Use' and trademark infringement when incorporating competitor names into product descriptions hinges on whether the use is descriptive and non-deceptive, or if it creates consumer confusion or implies endorsement. 'Fair Use' allows the use of a competitor's trademark to accurately describe a product's compatibility or intended use, without suggesting affiliation or endorsement. For example, stating 'Compatible with [Competitor Brand] printers' is generally considered Fair Use if the product genuinely works with those printers. Trademark infringement, however, occurs when the use of a competitor's trademark is likely to cause consumer confusion about the source, origin, or sponsorship of the product. This could involve using the competitor's trademark in a way that implies the product is made by or endorsed by the competitor, or if the use deceives consumers into thinking they are buying the competitor's product. The key is whether the use is purely descriptive and avoids creating any misleading impression about the relationship between the products or brands.