I would have to say Chinese since most number. But alot of Chinese are learning English, so English for the future win.
The language of love. hehe! Seriously, i think it's English. By common, you mean, majority of the nationality can speak or understand it.
Chinese for sure is the most spoken language in the world, but most common certainly has to be English.
MACHINE language. EVERY computer in the world uses machine language even though you don't see it because of the overlaid OSs.
People who speak: English: 1.5 billion Mandarin: 1 billion Spanish: 500 million Arabic: 450 million Hindi: 400 million
English, by and large, bridges more people from different corners of the globe and can be safely considered as the most common language.
English is the most popular one,and chinese is spoken by most most people in the world. and more and more people trying to learn chinese.