Indo-European, by a wide margin. Sino-Tibetan is a fair contender, since there are so many Chinese, but it has few descendents.
Swahili is the most spoken language in the Bantu family of languages. It is spoken by over 100 million people primarily in East Africa as a first or second language.
English is the language most spoken as their second language.
In 1960, the second most spoken language in the United States was Spanish.
The number of second language speakers, Ethnologue says, and no one put that into question.
Chinese (Mandarin)
Bohemia is part of the Czech Republic...the language spoken today is CzechCzech
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By far, the most widely distributed language family is the English language. English is spoken in 67 different countries.
Spanish.
The Germanic family, which includes English, German, Dutch, and Yiddish.
As of 2009, Mandarin Chinese is the most widely spoken language in the world. It has over a billion speakers, mostly in China.
The most spoken language is Chinese, then the second most spoken is English, and the third most spoken language is Spanish.