The feeling of being serious and not happy.
Solemnity is often connected to important events or ceremonies.
Examples:
The solemnity of the ceremony made everyone quiet.
The king's face showed solemnity during the ceremony.
She felt the solemnity of the moment.
The solemnity of the situation made everyone stop and think.
The solemnity of the judge made everyone feel nervous.
The solemnity of the event will stay in my mind forever.