“Likelihood of confusion” is a term of trademark law that is used to determine whether one trademark infringes another. Trademark rights prevent the use of a name, symbol, or other device where it is likely to cause confusion to a consumer about the source of a good or service – i.e., where there is a likelihood of confusion. 

An example where there is almost always a likelihood of confusion is in counterfeiting – selling fake Prada is obviously trademark infringement because many consumers are likely to be confused into believing that the knockoffs came from Prada.

Other cases can be more difficult, and courts use a multi-factor test to examine whether two similar trademarks are likely to cause confusion. Relevant factors include the similarity of the trademarks and similarity of the goods and services with which the trademarks are used. Suffice it to say there can be situations in which two identical trademarks may be unlikely to confuse consumers, and situations in which two similar but definitely not identical trademarks will be likely to confuse consumers.