The word 'unsustainability' is a modern English formation built upon the core concept of 'sustain'. The Latin root 'sustinēre' literally meant "to hold up from below," conveying the idea of providing foundational support. By adding the suffix '-ability', this action transforms into the abstract noun 'sustainability', denoting the capacity for enduring support. Finally, the Germanic prefix 'un-' is attached to negate this capacity, creating a term that precisely defines the inability to maintain a system or process over the long term, a concept central to ecological and economic discourse.

Structure: un (not) + sustain (support) + ability (capacity) - un: A prefix of Germanic origin (Old English 'un-'), meaning "not," used to form negatives. - sustain: A verb from Old French 'sustenir', ultimately from Latin 'sustinēre' ('sub-' from below + 'tenēre' to hold), meaning to support, hold up, or maintain. - ability: A noun-forming suffix from Old French '-ableté', from Latin '-abilitās', indicating a capacity, fitness, or quality.