The abstract quality or feeling of being sad; often used in emotional or literary contexts.
His singing voice was filled with deep sadness.
I cannot put the sadness of parting into words.
悲しさ is sadness or grief over something specific, while 寂しさ is the emptiness of being alone or missing someone, and the two feelings are often confused.
Standard kanji spelling for sadness.
Alternate kanji spelling; 哀 carries a nuance of pathos or pity.
Derived from the adjective 悲しい (sad) with the nominalizing suffix さ, forming an abstract noun meaning 'sadness'.