e·phem·er·al / əˈfem(ə)rəl/ • adj. lasting for a very short time: fashions are ephemeral. ∎  (chiefly of plants) having a very short life cycle.DERIVATIVES: e·phem·er·al·ly adv.e·phem·er·al·ness n.

ephemeral
1. Short-lived, or of brief duration (e.g. the life of a mayfly, Ephemeroptera).

2. (ephemerophyte) A plant that completes its life cycle very rapidly. In favourable environments ephemerals may germinate, bloom, and set seed several times during a single year. Many weed species are ephemerals. Ephemerals are also particularly characteristic of desert environments. The word is derived from the Greek ephemeros, meaning ‘lasting for only a day’.

ephemeral
1. (in botany) An annual plant that completes its life cycle in considerably less than one growing season. A number of generations can therefore occur in one year. Many troublesome weeds, such as groundsel and willowherb, are ephemerals. Certain desert plants are also ephemerals, completing their life cycles in a short period following rain.

2. (in zoology) A short-lived animal, such as a mayfly.

ephemeral existing only for a day or a very short time. XVI. f. Gr. ephḗmeros (whence fem. and n. in -a, -on as sbs.), f. EPI- + hēmérā day; see -AL1.
So ephemeris table showing the places of heavenly bodies for every day of a period XVI; astronomical almanac XVII. — L. — Gr. ephēmerís diary.

ephemeral (ephemerophyte) A plant that completes its life cycle very rapidly. In favourable environments ephemerals may germinate, bloom, and set seed several times during a single year. Many weed species are ephemerals. Ephemerals are also particularly characteristic of desert environments.