e·phem·er·a (/ɪˈfɛm(ə)rə, -ˈfiːm-/) plural noun

1. Things that exist or are used or enjoyed for only a short time.

“There were papers, letters, old boxes — all sorts of ephemera.”

(oed.com)

2. How some psycho girls think of boys: used only for a short time.

“Hi. I’m Caroline. I like that boy. I’ll add him to my list of ephemeras.”

(urbandictionary.com)