ephemeron

The word "ephemeron" refers to something that lasts only a very short time, often with the sense that it appears, shines for a moment, and is soon gone. It comes from Greek roots meaning "lasting only one day." The word was first used for short-lived things in nature, especially creatures such as mayflies, whose adult lives are famously brief.

From there, the meaning widened. An ephemeron can be almost anything temporary: a flash of beauty, a short mood, a passing social craze, morning mist, or a rainbow that disappears as suddenly as it came. The word is not common in everyday speech, but it shows up in literary, reflective, and academic writing when the writer wants to draw attention to how brief an experience or object is.

It often carries more feeling than a plain word like "temporary." It suggests not just short length, but also fragility and the sense that something is easy to lose. That is why it works well for moments, sights, and experiences that feel vivid precisely because they do not last.

You may also meet the related plural form "ephemera," especially when people talk about printed or written items that were made for short-term use, such as tickets, flyers, posters, or pamphlets. That related use is common, but for "ephemeron" itself, the central idea is still the same: something brief, passing, and soon gone.