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ephemera

noun, plural e·phem·er·as, e·phem·er·ae [ih-fem–uh-ree] /ɪˈfɛm əˌri/ for 2.

a plural of ephemeron.
an ephemerid.

noun, plural e·phem·er·a [ih-fem-er-uh] /ɪˈfɛm ər ə/, e·phem·er·ons.

anything short-lived or ephemeral.
ephemera, items designed to be useful or important for only a short time, especially pamphlets, notices, tickets, etc.

noun plural -eras or -erae (-əˌriː)

a mayfly, esp one of the genus Ephemera
something transitory or short-lived
(functioning as plural) a class of collectable items not originally intended to last for more than a short time, such as tickets, posters, postcards, or labels
a plural of ephemeron

noun plural -era (-ərə) or -erons

(usually plural) something transitory or short-lived

late 14c., originally a medical term, from Medieval Latin ephemera (febris) “(fever) lasting a day,” from fem. of ephemerus, from Greek ephemeros “lasting only one day, short-lived,” from epi “on” (see epi-) + hemerai, dative of hemera “day,” from PIE *amer- “day.”

Sense extended 17c. to short-lived insects and flowers; general sense of “thing of transitory existence” is first attested 1751. Cf. Greek ephemeroi “men,” literally “creatures of a day.”

1620s, from Greek (zoon) ephemeron, neuter of ephemeros (see ephemera). Figurative use by 1771.