A competitor who uses a trademark that is confusingly similar to an existing trademark can be prevented from doing so by the application of trademark law based on the "likelihood of confusion".
In determining likelihood of confusion, courts evaluate several factors. No one factor is determinative in and of itself, and how important one factor is over another is very case specific. The factors are:
-Whether or not the goods or services using the same mark compete with one another. Marks that are used on similar or related goods or services are more likely to confuse consumers as to the source of those goods or services. Even where the plaintiff's products are not exactly similar, the court may in some cases consider how likely the plaintiff is in the future to sell similar products.
-Whether or not the goods or services are so closely related that they are being marketed through the same stores or channels of distribution.
-Whether or not the alleged infringer intended to trick consumers in order to "cash in" on the plaintiff's business good will.
-Whether the marks are similar in appearance, phonetic sound, or meaning.
-How careful the consumer is likely to be prior to purchasing. The more sophisticated the consumer (e.g. business owners versus children), or the more expensive the product, then the more discriminating the consumer is expected to be, and the less likely confusion will be attributed to them).
-Whether or not the companies are accessing overlapping customer bases. If the companies both sell largely to senior citizens, to teachers, or to home-based business owners, there is more likely to be consumer confusion.
-The legal strength of each of the marks. The greater the public recognition of a mark as a source identifier, the more likely that similar uses will be confusing.
-Whether there has been any actual confusion. If so, this is not conclusive evidence of likelihood of confusion, but must be weighed together with the other factors.
