Etymology: Made up of two Japanese characters. The first, “yu,” means dim or difficult to see. The second, “gen,” originally described the dark, tranquil color of the universe—something calm and deep.

Meaning: The meaning depends on the context; the explanation most commonly offered is an awareness of the universe that triggers an emotional response too deep and mysterious for words. You may find that definition opaque, but it is an attempt to explain in words something that is fundamentally ineffable. Or you may feel a spark of recognition somewhere deep within. This is likely a feeling you’ve experienced but never before had a word for.

To best wrap your head around a word that words fail, it’s better to contemplate less its literal meaning and more the situations th...