Is "winter solstice" an affirmative sentence or a subject-predicate sentence in modern Chinese? The key is the meaning of' want', teacher.

Like the solstice in summer, the solstice in winter is a positive phrase, which means the shortest day in winter.

Your teacher said it means "extreme" and "final", which is not clear.

This "solstice" is a noun which means solstice (the shortest or longest day).

Winter solstice, the shortest day and the longest night in winter; Summer solstice, the longest day and the shortest night in summer.