ennui
UK[ɒnˈwiː]US[ˌɑːnˈwiː]
n
A feeling of listlessness and dissatisfaction arising from a lack of occupation or excitement.
Etymology
The word 'ennui' was borrowed into English from French in the mid-17th century, carrying its sense of profound weariness and boredom. The French term itself evolved from the Old French verb 'enoier', meaning 'to annoy', which traces back to the Late Latin phrase 'in odio esse' (to be hateful or odious). This Latin phrase is composed of 'in' (in) and 'odium' (hatred). Thus, the etymological journey moves from the concrete state of being an object of hatred, through the sense of being vexed or annoyed, to arrive at the modern, more abstract psychological state of listless dissatisfaction and mental weariness.
Analysis
The word is a simplex loanword from French. It cannot be meaningfully segmented into productive morphemes within modern English spelling.
Examples
A pervasive sense of ennui settled over the quiet, uneventful town.
The endless meetings filled him with a deep ennui.
She tried to combat her ennui by taking up a new creative hobby.