apathy; indifference; listlessness
General lack of emotion or interest; can describe a person's state or an atmosphere.
He listened to the news with an apathetic expression.
athymia
Medical term for a loss or absence of emotion; used in psychiatric contexts.
His indifferent attitude made those around him uneasy.
Athymia is known as one of the negative symptoms of schizophrenia.
Compound of 無 (mu, 'without') and 感情 (kanjō, 'emotion').