阴沉 is deeply connected to the philosophical concept of Yin-Yang (阴阳). While Yin energy (阴) is a natural and necessary force associated with quiet, darkness, and receptivity, an excess of it, as implied by 阴沉, suggests an unhealthy imbalance. It's a state where the bright, active, and warm Yang (阳) energy is completely suppressed, leading to a feeling of stagnation, coldness, and oppression.
Comparison with “Gloomy”: In English, “gloomy” can describe weather or a mood. 阴沉 carries a similar meaning but often feels more intense and visceral due to the character 沉 (chén), “to sink.” It’s the difference between a neutral gray day and a day with a low, dark, oppressive ceiling of clouds that feels like it’s physically pressing down on you. When describing a person, “gloomy” might suggest sadness, whereas 阴沉 often implies a sullen, withdrawn, and potentially resentful or angry state.