The character 天 tiān means “heaven, sky” - the blue skies above us, as well as the more metaphysical “infinity”. Tiān has also come to stand for a period of time, “a day”.

In this character we can first see the picture of a man, 人 rén. It is derived from a picture depicting a man standing with his legs apart. Earlier you could also see more details of the body and head, but with time the character has got more streamlined... just for the sake of elegance and convenience. Now, picture this man spreading his arms wide open and what do you see? Something “big”, 大dà, the meaning is very obvious here!

But, above this great man there is still the “sky”, 天 tiān. The heavenly dimension is pointed out by drawing a line above the man's head.