unhappiness
n.the feeling of being sad or not satisfied with your life. It is the opposite of happiness.
n.the state of being sad, miserable, or dissatisfied. Uncountable in its general sense; countable when referring to specific instances or types of distress.
“She couldn't hide her unhappiness with the new rules.”
“The survey aims to measure the level of unhappiness among employees who work long hours without breaks.”
“While wealth can provide comfort, it is rarely a permanent shield against the deep-seated unhappiness that stems from a lack of purpose or social connection.”
Often paired with the preposition 'about' or 'with' to indicate the cause of the feeling.
From unhappy + -ness or un- + happiness.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.