fugacious

This is a high-register, literary term that evokes a sense of fragility and inevitable loss. It describes something that doesn't just end, but slips away or evaporates quickly.

While 'fleeting' is common in everyday speech, "fugacious" carries a more melancholic or philosophical weight. It suggests a poignant awareness of time passing, often used when discussing beauty, youth, or memory.

In botanical contexts, the word is technical and precise, describing parts of a plant that are designed to drop off early in the life cycle, shifting from a poetic feeling to a clinical observation.