traditional: 天
simplified: (same)
Pinyin: tian [1st sound]
Definition: sky, day, heaven

“天” is “top” in original word, means “top of the head”. And the upper position of the head is the sky, so “天” would be use as “sky” or “heaven”. This word in the Bronze engraving script (jin wen) has a big round marking, the Oracle bone script (jia gu wen) marks as rectangular shape. After, the marking use only horizontal line.