Sun, The Sun, Sol
noun
The fat sunshine thing up in the sky... what is it called? Oh, that's right. It's the sun.
たいよう
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
あっ、太陽の光が出てきましたね。
Oh, the sun has come out.
太陽の温度って何度ぐらいあるか知っていますか？
Do you happen to know what the sun's temperature is?
日本万国博覧会のシンボルは、岡本太郎が作った「太陽の塔」で、それは今も日本の大阪の吹田にある万博公園にそびえ立っています。
The symbol of Expo ’70 was the Tower of the Sun, created by Taro Okamoto, and it’s still standing in the Expo Commemoration Park in Suita, Osaka, Japan.