ephemˈeral adjective

1. Existing only for a day
2. Short-lived
3. Fleeting

Anything very short-lived

ephemeralˈity noun

ephemerally adverb

ephemˈeralness noun

ephemˈerid noun

An insect of the mayfly family Ephemerˈidae /-merˈi-dē/ (order Ephemeropˈtera)

ephemeridˈian adjective

ephemˈeris noun (pl ephemerides /ef-e-merˈi-dēz/)

1. An astronomical almanac tabulating the daily positions of the sun, moon, planets and certain stars, etc
2. An individual table showing this
3. An account of daily transactions (archaic)
4. A journal (archaic)

ephemˈerist noun

1. Someone who studies the daily motions of the planets
2. A student or collector of ephemera

ephemˈeron noun (pl ephemˈera)

1. An insect that lives only for a day
2. (usu in pl) an object of limited worth or usefulness, having no lasting value
3. Anything ephemeral

ephemˈerous adjective

ephemeris time noun

Time measured by orbital movement of earth, moon and planets, differing from mean solar time in that it allows for irregularities due to variations in rate of rotation of the earth, an ephemeris second being a fixed fraction of the solar year 1900