Jenny Lederer, assistant professor and linguistics advisor in the Department of English Language and Literature at San Francisco State University: "Semantics is the study of meaning in context; it's the investigation of how words, phrases and sentences evoke concepts and ideas in our minds. As we learn language, we attach meanings to words by learning what objects and concepts each word refers to.
"'It's just semantics' is a common retort people use when arguing their point. What they mean is that their argument or opinion is more valid than the other person's. It's a way to be dismissive of language itself as carrier for ideas. It implies that ideas and arguments can be separated from the words and phrases used to encode those ideas. The irony, of course, is that the words and phrases we use are the ideas. There is no way to communicate a complex argument or message without language. Language and thought are completely interconnected. In fact, words shape concepts and can lead to drastically different understandings of the same thing. For example, inheritance taxes can be called 'death taxes' or 'estate taxes.' These two political phrases frame the same tax law in drastically different ways. Semantics really matters."
Robert Henderson, Associate Professor of Linguistics at the University of Arizona: "Semantics is the study of meaning very broadly. We have semantics for human languages, but also for logics, or computer languages. In the case of human languages, to have a semantics for a language is to be able to assign a meaning to every word in that language, and then to compute the meanings of sentences based on the meanings of those words and how they are put together.
"The phrase, 'that's just semantics,' is thus a little confusing. People seem to use it when they want to say that the disagreement they're currently having is due to word choice and not due to a substantive disagreement. But that is not semantics at all. That would be, like, lexicography. The reason this phrase has nothing to do with actual semantics is that if we were having an argument that boiled down to 'just semantics,' then we would be having an argument about what words mean. But that is not insubstantial at all! In fact, it is incredibly important for us to figure out what the various parties to an argument actually mean if we hope to resolve it. So, what is going on here? I think that it seems that in popular parlance, people use 'semantics' to mean something like 'nitpicky distinctions.' That is, in the popular use, when I dive into the semantics of what you're saying, I'm closely parsing every little thing. Thus, if we are having an argument and it's 'just semantics,' then what you're saying is that we're having an argument over fine, nitpicky details that don't matter. I don't like this use because I'm a semanticist, and that is not what I do at all. I do logic, actually. But, what can you do? People will speak the way people speak."
Dylan Bumford, assistant professor in the Department of Linguistics at UCLA: "There are various technical notions that go by the name 'semantics.' Mostly, they are trying to characterize the ways that linguistic forms (like logical formulas, or computer programs or sentences in English) are, or ought to be, associated with the things they describe. In logic, this often takes the form of rules that match formulas with mathematical structures. In computer science, programs may be associated with procedures for transforming machine states. In philosophy and linguistics, you might find English expressions matched up with specific objects and scenes, or at least representations of these. Outside of these research fields, my sense is that people use the word 'semantics' to describe very fine distinctions between different categories, especially if those distinctions are so subtle as to be irrelevant. In this sense, 'semantics' would be something like the art of making annoyingly precise or pedantic linguistic choices.
"I take it when most people describe an argument as a 'matter of semantics,' they mean that the two sides are effectively saying the same thing, or that the difference between them is negligible; the positions differ only in the words that are used (to some, this would make it a matter of syntax, not semantics; but of course, to others, that very difference might be a matter of semantics). Sometimes, though, discussions really are about the meanings of words. If two people agree on all the facts — they know who did what to who, and what happened when, etc. — but they still disagree on whether a certain sentence is true, they may be having a genuine debate about semantics, about what objects or situations should be associated with various expressions. For instance, if we disagree about whether Donald Trump withheld military aid in an effort to persuade the Ukrainian prime minister to launch an investigation into Trump's political opponents, we are having a substantive disagreement about what actually happened, about what the world is like. But if we agree that he did this, yet nevertheless disagree about whether such an action constituted a 'quid pro quo' or 'high crime,' we might instead be having a debate about semantics. As should be clear though, in this sense, semantic disputes can indeed be very big deals!"
Shane Steinert-Threlkeld, assistant professor in the Department of Linguistics at the University of Washington: "Semantics is the scientific study of meaning as expressed in language. Usually, this means doing things like explaining formally under what conditions sentences in natural languages are true or false, or when one sentence implies or presupposes another. The methods can also be applied to formal languages like programming languages, where one would explain, for example, how a computer program will behave.
"Indeed, a difference in a debate that came down to 'just semantics' would be a pretty big deal, since it means that we're using expressions in different ways. There seems to be a use of the phrase that means something more like 'this dispute is merely verbal: we actually agree, but we appear to disagree because we are using certain terms in slightly different ways.' I'm not sure that 'just semantics' is a particularly apt way of expressing that thought, but it's one that some people seem to use."
Toshiyuki Ogihara, professor and graduate program coordinator in the Department of Linguistics at the University of Washington: "In most cases, when people say that it is just semantics, they mean that two expressions refer to the 'same situation' or 'same thing' but their connotations are different."