Trademark infringement is generally unauthorized use of a mark in commerce that is likely to confuse consumers about the source, sponsorship, or affiliation of goods or services. Identical wording is not required. Courts examine the marks, products, customers, sales channels, evidence of confusion, and other circumstances.
Owning a registration helps, but it does not make every similar use unlawful. The practical question is whether the challenged use interferes with the trademark’s source-identifying function.
The core elements of an infringement claim
A plaintiff usually must establish a protectable trademark right, priority over the defendant in the relevant market, and a likelihood of confusion. A federal registration can provide important procedural and evidentiary benefits. Earlier common-law use may still matter.
The USPTO explains that likelihood of confusion is assessed under multiple factors and that the particular evidence controls. The exact factor test and weighting vary by federal circuit. See the USPTO’s infringement overview.
Similarity is broader than an exact match
Courts may compare appearance, sound, meaning, and overall commercial impression. Similarity matters more when the parties offer closely related products through the same channels. A shared ordinary word may receive less weight if the rest of each mark creates a different impression.
Example: Assume one company uses NORTHSTAR for bookkeeping software and another later uses NORTH STAR LEDGERS for closely related cloud accounting services. The analysis would consider the marks as a whole, the related services, customers, channels, and evidence. This hypothetical does not mean either name is legally available.
Evidence that often matters
- How and when each party began using the mark
- Registrations, applications, packaging, websites, advertisements, and sales records
- The strength and marketplace recognition of the senior mark
- Actual confusion, including misdirected communications or support requests
- The defendant’s intent, where relevant under the governing circuit’s test
- Differences in customers, price, purchasing care, geography, and sales channels
Preserve original files, dates, URLs, screenshots, invoices, analytics, customer messages, and product samples. A dated evidence file is usually more useful than a later narrative reconstructed from memory.
Defenses and lawful uses
A defendant may dispute validity, ownership, priority, use in commerce, or likely confusion. Depending on the facts, descriptive fair use, nominative reference, consent, license, acquiescence, laches, or other defenses may apply. These doctrines are fact-specific and vary across jurisdictions.
Possible remedies
The Lanham Act authorizes remedies that may include injunctions, recovery of certain profits or damages, costs, destruction or disposition of infringing materials, and attorney fees in exceptional cases. The remedy depends on proof and equitable principles; it is not automatic. Review 15 U.S.C. § 1117 and 15 U.S.C. § 1118.
What to do if you suspect infringement
- Confirm your ownership, priority, registration status, and current use.
- Capture the challenged use and identify who controls it.
- Assess confusion, defenses, business harm, and the desired outcome.
- Choose a proportionate response, such as monitoring, outreach, a coexistence discussion, a platform report, or litigation.
- Have counsel review the evidence before making accusations or threatening suit.
Read next: what to do when someone is using your business name and how to respond to a trademark cease-and-desist letter.
The practical next step
Build a short chronology of both parties’ use and collect the actual marketplace materials. A trademark lawyer can then evaluate the governing circuit’s factors, potential defenses, and a response calibrated to the business risk.