When it comes to the world's ten most spoken languages, numbers tend to vary considerably between sources. According to Ethnologue, Chinese (and all of its varieties such as Mandarin and Wu) is by far the most spoken language across the world with 1.31 billion speakers. That's approximately 16 percent of the world's population. Indeed, there are between 7 and 13 main regional groups of the Chinese language and Mandarin is the most spoken (898 million speakers).
Widely spoken in South America as well as Spain, Spanish is the planet's second most widely spoken language with a grand total of 460 million speakers according to Ethnologue. English has 379 million speakers while Arabic has 319 million. The latter includes 19 different varities, of which Egyptian Arabic is the most spoken (64.5 million speakers), followed by Algerian Arabic (29.3 million speakers).