Ennui
Part of speech: noun
Definition: A gripping listlessness or melancholia caused by boredom; depression.
Example sentence: The song 'Take This Job and Shove It' spent 18 weeks on the country charts in 1977. 1970s country music fans had a clearer understanding of the ennui of wage-slavery than modern elites.
Tedium
Part of speech: noun
Definition: boredom or tediousness; ennui