Ephemeral‏ [Noun.]

Something which lasts for a short period of time.

“And so castles made of sand slip into the sea, eventually.” – Jimi Hendrix

Ephemeral was originally a medical term with the specific meaning ‘lasting only one day’, as a fever or sickness (Hemera means ‘day’ in Greek.) The word became more general, coming to mean ‘lasting a short time’, covering the life spans of plants or insects and then eventually anything that is fleeting or transitory.

“Patriotism is an ephemeral motive that scarcely ever outlasts the particular threat to society that aroused it.” – Denis Diderot