decline

A gradual and continuous loss of strength, numbers, quality, or value. While Japanese has specific terms for various types of decrease or deterioration (e.g., 減少 for numerical decrease, 衰退 for decay, 低下 for falling quality), there isn't a single noun that covers the full range of meaning and contexts (such as economic, social, moral, and physical) as broadly as the English word decline, often requiring a more specific term depending on the situation.

• The country's economy has been in decline for several years.
• There was a sharp decline in the number of tourists during the pandemic.

To politely refuse to accept something or to do something (e.g., an offer or invitation), or to gradually decrease in amount, strength, or importance. In Japanese, these two primary meanings are typically expressed by different verbs: 断る or 拒否する for refusing, and 減少する or 悪化する for decreasing or deteriorating, as there is no single verb that encompasses all nuances of both 'refusal' and 'deterioration/decrease' as decline does in English.

• She had to decline the invitation due to a prior engagement.
• The patient's condition began to decline rapidly.