How could you use the word ennui as a noun in a sentence?

A noun functions as the subject of a sentence or a clause, and as the object of a verb or a preposition.

Examples:

Her ennui made it difficult for her to study. (subject of the sentence)

The mood that the ennui produced sapped her ambition. (subject of the relative clause)

We could see the ennui in his body language. (direct object of the verb 'could see')

He was plagued by ennui after a death in his family. (object of the preposition 'by')