fleetingness

From fleeting +‎ -ness.

fleetingness (countable and uncountable, plural fleetingnesses)

1. The quality of being fleeting.
   • 1709, George Berkeley, An Essay Towards a New Theory of Vision, §156:

     But the perpetual mutability and fleetingness of those immediate objects of sight render them incapable of being managed after the manner of geometrical figures […]

• (transience): ephemerality, briefness, transiency; see also Thesaurus:transience