To determine whether or not a particular use by a defendant is likely to cause confusion with a plaintiff's trademark, courts look to various factors. While these factors vary somewhat with the location of the court, they are essentially:

• the similarity in the overall impression created by the two marks;
• the similarity of the goods and services involved;
• the strength of plaintiff's mark;
• any evidence of actual confusion by the consuming of such goods and or services;
• the intent of defendant in the adoption of the mark;
• the physical proximity of the goods in the retail marketplace;
• the degree of care likely to be exercised by the consumer; and
• the likelihood of expansion of product lines.

There are, of course, varying degrees within the above factors. In some situations, there is no need to consider the factors because confusion is either extremely likely or extremely unlikely. For example, if you were to attempt to trademark Coke for any type of beverage, confusion would be considered likely.

The abovementioned factors become important in situations which are less defined. For example, using the factors above, a court held that dentists using "McDental" could cause confusion with "McDonald's", the burger factory. This conclusion shows the susceptibility of the factors to a high degree of personal opinion while evincing that certain factors can easily swallow others. In particular, the McDonalds make has overwhelming strength, overwhelming enough to overcome the other factors, such as the physical proximity, degree of care and the similarity of the goods and services, among others.