Which solar term is relative in winter?

This solar term is relative to the summer solstice.

Winter solstice and summer solstice are two important solar terms in the 24 solar terms, which are located at the extreme positions of winter and summer respectively. The origin of winter solstice solar terms can be traced back to ancient China, which is determined according to the position of the sun on the ecliptic. From winter to the sun, the sun is located at 270 degrees of the yellow meridian, and the sunlight almost directly reaches the Tropic of Capricorn, which has the shortest day in a year in the northern hemisphere. Accordingly, the winter solstice in the southern hemisphere has the longest day.

The winter solstice is the beginning of winter in the northern hemisphere, and it is also the time when yin and yang alternate in a year.