The opposite of 태양(太陽) is 태음(太陰), which is a sino-Korean word for "the moon." It literally means "big shadow." 태(太) means "big," and 음(陰) means "shade" or "shadow." The pure Korean word for "the moon" is 달.
The Chinese characters 양(陽 - light) and 음(陰 - dark) form the word 음양(陰陽), which refers to the philosophy that everything in the universe has an opposite. The Chinese call it "yin-yang."
Here are more words that use the Chinese characters 음(陰) and 양(陽):
- 양력(陽曆) - solar calendar
 음력(陰曆) - lunar calendar
 .
- 양지(陽地) - a sunny place
 음지(陰地) - a shady place
 .
- 양성(陽性) - positive
 음성(陰性) - negative
 .
- 양수(陽數) - a positive number
 음수(陰數) - a negative number
 .
- 양극(陽極) - a positive pole (electricity)
 음극(陰極) - a negative pole (electricity)
 .
- 양각(陽刻)하다- emboss (carve in relief)
 음각(陰刻)하다 - engrave
If anyone can think of more words, I will add them to the list.
 
