Nouns

(n)ephemeron, ephemeralanything short-lived, as an insect that lives only for a day in its winged form

Adjectives

(s)ephemeral, passing, short-lived, transient, transitory, fugaciouslasting a very short time“the ephemeral joys of childhood”, “a passing fancy”, “youth's transient beauty”, “love is transitory but it is eternal”, “fugacious blossoms”