In trademark law, the similarity between goods or services refers to how closely related or interchangeable they are in terms of their nature, purpose, or intended use. The degree of similarity between goods or services is a critical factor in determining whether there is a likelihood of confusion between two trademarks.
If two trademarks are found to be confusingly similar, the owner of the later trademark may be prevented from using it, or they may be required to modify it to avoid confusion with the earlier trademark. Conversely, if the goods or services are not similar, then there is a lower likelihood of confusion between two trademarks, and the owner of the later trademark may be allowed to use it.
When evaluating the similarity between goods or services, courts and trademark offices will consider various factors, including the nature and purpose of the goods or services, the channels of trade used to sell them, the target consumers, and the overall impression created by the trademarks. The more similar the goods or services are, the more likely it is that there will be a likelihood of confusion between the trademarks.