Many of the words we’ve dissected here have faded almost entirely from public consciousness. They’re used less commonly over time, and then favored by English purists and journalists, but remain unknown to, or unused by, the average person. However, some words have managed a sort of duality, in which they simultaneously maintain their significance and remain somewhat hidden. One such word is isthmus.

Most of us learn about isthmuses in early geography classes. An isthmus is officially defined as “a narrow strip of land connecting two larger land areas”. Some of the most well-known isthmuses include the Isthmus of Panama, which connects North and South America, the Isthmus of Suez, which connects Africa, via eastern Egypt, to Asia, and the city of Seattle, which lives on an isthmus connecting Lake Washington and the Puget Sound.

Isthmus first surfaced in the 1550s and was derived from both the Latin word isthmus and Greek word isthmos. Isthmos, more or less, had the same meaning — a narrow neck of land between two seas.

Beyond geography classes, isthmus is reserved for niche uses. There’s a Madison, Wisconsin-based publication titled Isthmus, which covers local news, politics, and culture. The name honors the Madison Isthmus, which separates Lake Monona and Lake Mendota, and connects the city’s east and west sides.

Here, we see isthmus following a similar pattern, in which it serves a purpose, but loses its prominence over time. However, the difference is that isthmus remains relevant for school age children and teachers. Its importance may be reduced as those students age, but it remains in history books — it’s a part of a cycle that will always keep it alive.

Another way that isthmus differs from other words is the power of its alternate definition. Isthmus is also defined as “a narrow anatomical part or passage connecting two larger structures or cavities”. For medical students and professionals, isthmus remains an active part of their vocabulary long after they’ve finished their last geography course.

The isthmus of the thyroid connects that organ’s two lobes and even covers two rings of the windpipe. Some people are born without a thyroid isthmus (agenesis) or lose it due to trauma. When the isthmus is missing or damaged, it can lead to thyroid abnormalities. Thus, it has been identified as a possible risk factor in thyroid cancer.

In early 2018, the aortic isthmus was identified as a way to spot signs of heart failure on children’s echocardiograms.

And aside from these isthmuses, the human body possesses several others — the isthmus of the auditory tube, the pharyngeal isthmus, and the isthmus of the uterine tube, to name a few. In some ways, even though we may not speak about isthmuses in everyday conversation, they play a more significant role in our lives than many of us will ever realize.

Isthmus maintains its relevance by serving needs at both ends of the spectrum — it’s a crucial part of our early geographical education, which we rarely use once we get older, and it’s actively used by a niche audience. Unlike so many words that slip from our memories as we get older, it seems isthmus will never fade entirely from our consciousness. It’s a word that remains important, even when many of us stop using it.