What do big and small colds mean?

Large and small cold refers to great cold and slight cold, and refers to the solar terms of cold weather and extremely cold weather. The Great Cold is the last of the 24 solar terms. Slight cold is the 23rd solar term in 24 solar terms and the 5th solar term in winter.

After the winter solstice, the cold air frequently goes south, and the temperature continues to drop, and the temperature drops to the lowest during the slight cold and severe cold in a year. In the slight cold season, the direct point of the sun is still in the southern hemisphere, and the heat in the northern hemisphere is still in a state of loss. The heat absorbed during the day is still less than the heat released at night, so the temperature in the northern hemisphere continues to decrease.