Refers to a state of not being active, often used in medical or formal contexts to describe physical or mental sluggishness.
Prolonged inactivity leads to muscle weakness.
Inactivity can be seen as a symptom of depression.
停滞 implies stagnation or a halt in progress, often used for economic or social contexts, whereas 不活動 is more about a general state of not being active.
Compound of 不 (fu, 'not') and 活動 (katsudō, 'activity'). The exact historical derivation is uncertain, but the word follows a common Sino-Japanese pattern for negation.