What is indicated by a wine becoming stale?

When a wine becomes stale, it typically indicates that it has been exposed to air over time, which leads to oxidation. This process alters the wine's chemical composition and negatively impacts its flavor and aroma profile. Fresh wines usually exhibit vibrant flavors and aromas, but with exposure to air, the wine can lose its lively characteristics and develop off-flavors that make it taste flat or lifeless. In contrast, proper aging of wine involves controlled conditions that promote desirable development without the negative effects associated with staleness due to excess oxygen. This is the core reason why the answer related to exposure to air is the one that accurately describes the phenomenon of a wine becoming stale.