If you're looking to expand your linguistic horizons while simultaneously setting yourself up for professional success, there's one language that vastly outpaces the rest in terms of its utility. As Emily Oster, associate professor of economics at Brown University, says, "Mandarin would be the best choice."

"This is the native language for 14 percent of the world's population," she explains, "and most of those people do not speak English, so it's all a win."

It's definitely a win, considering over one billion people speak it worldwide already, and China is slated to become the number one economic power on the planet by 2020.

In particular, speaking Mandarin makes you very attractive to multinational corporations. The rate of companies seeking executives who speak Mandarin has gone up by 35 percent of late.

The only catch? Unless you were raised bilingual, Mandarin (or Cantonese, for that matter) is really hard to learn. In fact, Mandarin is ranked the most difficult language in the world for English-speakers to learn, followed by Arabic and Japanese.

As professor of second language acquisition at the University of Maryland Robert DeKeyser says, if you're an adult "[y]ou cannot expect to just absorb language the way that a child does. Children are good at learning the underlying system of all the language input they get because they can infer the underlying patterns without understanding the rules. Adults must be conscientious of the rules of the language. Their implicit learning doesn't work all that well."

However, if you're looking for a job in China, you may not always be required to be totally fluent. Many Chinese companies look for a strong grasp of career and personal diversity, not just language skills.

Thus in addition to technical and managerial skills, they want people with a diverse work background as well as sense of cultural diversity.

In this case, diverse work experience means either an international education or work experience. In many cases, having already worked for a large multinational corporation is a plus.

Cultural diversity often means having experience working with distinct managerial and leadership styles. For example, having a genuine understanding of the Chinese concept of saving face will help.

The fact is, the global balance of power is shifting, and those who are the most flexible (able to cross over between cultures, both linguistically and practically) will be in the best position to succeed in the long run.