IPA: /dɪˈlɪrɪəsnəs/
KK: /dɪˈlɪrɪəsnəs/
A state of being confused and excited, often due to illness or extreme emotions.
After the long fever, he experienced a sense of deliriousness that made him see things that weren't there.
Deliriousness is formed from "delirious" (from Latin "delirare", meaning to be out of one's mind) and the suffix "-ness" (meaning the state or quality of). The word describes the state of being in a delirious condition or having a disturbed state of mind.
Think of being 'out of one's mind' ('delirare') to remember that 'deliriousness' refers to the state of having a disturbed mind.