Despite what we tell kids as they're learning to spell, “sounding it out“ doesn’t always work. In fact, if you say “sounding it out,“ chances are you won’t pronounce that last t. Dropping that t sound is an example of what linguists call glottalization: the sudden coming together of the vocal cords to block the flow of air, and then opening again. In other words, replacing a sound with a pause in the vocal cords.

In American English, the letter t is especially likely to be glottalized, and it can happen at the end or in the middle of words. In the middle of a word, it typically happens in one of two scenarios: when a t is before a consonant starting a new syllable (such as in Scotland or Batman) or when a t is before a syllable making the n sound (such as certain or kitten). Ts before a vowel sound, on the other hand, are almost never dropped, meaning words like gritty and meta are typically safe from this phenomenon.

T-glottalization exists in most English dialects, but it is most frequently heard (and likewise most studied) in dialects of British English. Completely dropping the ts in butter or water, for instance, would feel bizarre to an American—it sounds distinctly British. Yet, you rarely hear an American pronounce either of those words with a hard, crisp ‘t’ sound in the middle, either. Instead, many ts in American English are subject to a tactic between pronouncing and glottalizing: flapping. Flapping, in linguistics, refers to replacing a t sound with a quick, d-like sound. So, for Americans, butter ends up sounding more like “budder,“ and water ends up sounding more like “wadder.“

But not all British dialects feature t-glottalization. Famously, British Received Pronunciation—the “posh”-sounding British accent most often used for period pieces and by the royal family—pronounces every single t crisply. If you watch actors perform a William Shakespeare play, for example, you’ll probably hear t sounds loud and clear. It’s the effort to pronounce every t that helps distinguish the accent and give it its formal, upper-class perception, whereas t-glottalization is seen as much more casual in British English.

The glottalized t is so widespread that it even has its own phonetic symbol: ʔ. But why do we do it in the first place? No one knows, exactly, but most linguists assume that it’s for the same reason that many other linguistic quirks arise: it makes it easier and faster to communicate.

In fact, in America, t-glottalization seems to be on the rise. Young people are especially likely to swallow their ts, leading to more and more instances of Americans saying things like “impor-an” instead of important. For linguists, this is an important statistic; studies find that young people are usually the first to adopt new linguistic trends that later become commonplace. So before you make fun of your local Gen Z-er for dropping their ts in new places, remember that they’re “impor-an” linguistic innovators.

This article was originally published on www.mentalfloss.com as T-Glottalization: The Reason Some People Drop Their ‘T’s When Speaking.