When I was studying Spanish and had gotten to the point where our assignments consisted of reading real books, I kept a well-thumbed dictionary on my desk. Every paragraph seemed to contain several words that I had to look up, which was tedious and slow. Our wise teacher kept telling us that we didn't need to do that—you don't actually have to know what every word means to understand the text.

A few years later I encountered the essay "The Joy of Sesquipedalians" by Anne Fadiman, where she recounts how she read a book that was full of unfamiliar English words. This was such an unusual experience for her that she kept a list of the words she didn't know.

Since then I've occasionally done a similar exercise. As I'm reading, I'll monitor for terms I don't recognize. It's a fascinating experience, because it really underscores what our Spanish teacher was trying to tell us—there are many words that we don't know, and it's surprising how often we might skip over them if they don't seem critical to understanding a passage.

I've found that if I turn on my Spanish-studying mode while reading in English and obsess about every word in a sentence, I can assemble a list of a dozen unfamiliar (to me) terms very quickly. Below I've listed a few that I've encountered recently.

opisometer: A friend on Facebook was asking if anyone knew where she could find this tool. I recognized the device—I used to watch a friend's father use one while he was working—but didn't know its name. I'm slightly disappointed that if you go looking for one of these, you'll now find that it's more commonly called a "map measurer," since opisometer is such a fine word.

glurge: This is another term that came up on social media, in a discussion about dubious stories that get passed around in email. I didn't feel so bad about not knowing this term, since it's a relatively recent coinage.

orthopraxis: I was reading a piece about differences between religions, and the author noted that some tended to emphasize orthodoxy ("correct belief," a term I did know) while others tended to emphasize orthopraxy ("correct practice," a term I'd apparently never consciously seen).

dewar: This was in a book that discussed rockets, so I initially assumed it was a technical term. But it's what's more commonly referred to as a Thermos bottle, referencing its inventor.

labile: I ran across this term in an article in The New Yorker, a publication that's very much for general readers. It's a particularly good example of a term I would have skipped had I not been on the lookout for unknown words.

gibibyte: I ran across this term in the documentation that we create at my work, of all places. I initially assumed it was a spelling error (for gigabyte), and was quite surprised to discover that it's a term regularly used in my own industry. I feel slightly better about not recognizing the term since it's also not recognized by the spelling checker in Microsoft Word 2013.

I don't think of these terms as particularly obscure. On the contrary, I strongly suspect that I've encountered them before, but not while paying close enough attention. If I'm not undergoing one of my periodic exercises in obsessiveness, I am nearly blind to unfamiliar terms like these.

If you, like me, don't routinely work in Spanish-student mode and dive for the dictionary every single time you find a new term, I recommend this exercise highly. Obviously, your list of unknown terms will be different from mine (and from everyone else's), but I bet you can assemble a list of new terms pretty quickly. Not only does it build your vocabulary, but it reminds us how incredibly rich the English lexicon is. And, of course, it's a good reminder of how well we can read and understand what we're reading in spite of these strange terms in our midst.