An examining attorney can refuse your application for a long list of reasons, and they fall into two families that behave completely differently. Relative grounds are about somebody else: their rights collide with yours. Absolute grounds are about your mark itself, and would apply even if you were the only business on earth.
Knowing which family you are in tells you most of what you need, because the two are answered in entirely different ways.
The one that stops most applications: likelihood of confusion
Section 2(d) of the Lanham Act is the most common substantive refusal. If your mark so resembles a registered mark, used on related goods, that buyers would likely be confused about the source, it is refused. Note the three moving parts: resemblance, relatedness, and likelihood. None of them requires the marks to be identical or the goods to be the same.
This is the refusal that a proper clearance search exists to predict. It is also the one most often survivable, because the examiner is working from the register alone and has not heard your argument about why the goods are further apart than they look. The framework is in the DuPont factors, and the practical version is how similar is too similar.
Absolute grounds: problems with the mark itself
Merely descriptive, 2(e)(1)
The mark describes a feature, quality, ingredient, purpose or characteristic of the goods. CREAMY for yogurt. FAST for delivery. This is the second most common refusal and the one founders walk into most often, because a descriptive name feels like clear marketing.
It is not fatal, and there are two ways out. Argue the mark is suggestive rather than descriptive, which means it takes a mental step to get from the word to the product, and that step is the whole argument. Or accept the finding and claim acquired distinctiveness under section 2(f), which means proving buyers have come to treat the term as a brand. Five years of substantially exclusive use can support that claim; heavy advertising, unsolicited press and survey evidence support it better. The fallback is the Supplemental Register, which gives you far less but keeps a place in line.
Generic
The term is the common name for the thing itself. This one really is fatal, in every form, forever. No amount of use or money makes it registrable, because competitors need the word to say what they sell. A mark can also become generic through success, which is what happened to aspirin, escalator and thermos.
Primarily merely a surname, 2(e)(4)
Surnames are refused on the theory that others with the same name should be able to use it. The analysis looks at how rare the name is, whether anyone connected with the applicant bears it, and whether the word has any other recognised meaning. A surname can be registered under 2(f) after five years, and many well-known brands took exactly that route.
Geographic grounds, 2(e)(2) and 2(e)(3)
A mark that is primarily geographically descriptive, where the goods really do come from that place, is refused under 2(e)(2) and can be cured under 2(f). A mark that is geographically deceptively misdescriptive, where the goods do not come from the place and the connection matters to buyers, falls under 2(e)(3), and that one cannot be cured by 2(f) or saved by the Supplemental Register.
Functional, 2(e)(5)
A feature that exists because it works better cannot be a trademark, however distinctive it looks. This is what keeps trademark law from handing out perpetual monopolies on engineering. Functionality is absolute: no 2(f), no Supplemental Register.
Name of a living individual, 2(c)
A mark identifying a particular living person needs that person written consent. This catches founders using their own full name more often than people expect, and the cure is straightforward: file the consent.
Failure to function
Not everything printed on a product is a trademark. Widely used messages, common phrases and expressions that buyers read as decoration or sentiment rather than as an indication of source are refused because they do not function as marks at all. Ornamental use is the classic version: a slogan across the chest of a shirt is usually the product, not the brand on it.
The refusals nobody warns you about
Two more account for an enormous share of real office actions, and neither is about your name.
Specimen refusals. The specimen has to show the mark used in commerce, on the goods themselves or their packaging for products, and in connection with the services for services. Mock-ups, printer proofs, and pictures of a website that only advertises the goods without a way to buy them all get refused. This is the single most common avoidable problem in a first office action.
Identification and classification. An identification of goods that is too broad, uses vague language, or sits in the wrong class draws an objection. It is routine and usually easy, but it can be a trap: you may narrow an identification, never broaden it. An overly cautious first draft is permanent.
What happens after a refusal
A refusal is not a rejection. It opens a conversation with a deadline. For most applications the response period is three months from the issue date, with a single three-month extension available for a fee, a change that took effect in December 2022; applications filed through the Madrid Protocol keep the older six-month period.
Your realistic options are to argue, to amend, to claim 2(f), to move to the Supplemental Register, or to appeal to the Trademark Trial and Appeal Board. Which one fits depends entirely on which ground you are answering, which is why the first question is always which family the refusal came from.
The short version
Relative grounds can often be argued, because they depend on judgments about similarity and relatedness. Descriptiveness can usually be cured with time and evidence. Genericness, functionality and geographic deception cannot be cured at all. If you are choosing a name now rather than answering a refusal, that last sentence is the one worth remembering.