What's the difference between mega and M?

1M = 1 00000 =10 to the sixth power,1m is1trillion.

Zhao (pinyin: zhào) is a first-class Chinese character, which first appeared in Oracle Bone Inscriptions in Shang Dynasty. The original meaning of this word refers to the crack that indicates good or bad luck when the ancient people burned Oracle Bone Inscriptions in divination, and it is extended to omen and ominous sign.

Related information:

Signs are hieroglyphics. Initially, it came from the cracked hieroglyphics of tortoise shells burned by fire. Because of the similarity between symbols and related glyphs, there is a river image with the same meaning but different sounds. Therefore, in the Western Zhou Dynasty, some ancient Chinese characters (such as Yao characters) were used to refer to omen, but they could not be regarded as the mainstream of the development of omen characters. Because in the Warring States period, only a few characters were written in the form of quotations, and the vast majority of characters were developed on the basis of the Shang Dynasty structure.