The United States Foreign Service Institute and its language categorization

According to its official Facebook page, the U.S. Department of State: Foreign Service Institute “develops the men and women our nation requires to fulfill our leadership role in the world affairs and to defend U.S. interests.”

The FSI was founded on March 13, 1947, in compliance with the Foreign Service Act of 1946 passed by Congress. The Director of the Foreign Service Institute is equivalent in rank to an Assistant Secretary of State, and is appointed by the current Secretary of State.

United States Federal Government's primary training institution for officers and support personnel of the U.S. foreign affairs community, the FSI prepares American diplomats and other professionals to advance U.S. foreign affairs interests overseas and in Washington.

At the George P. Shultz National Foreign Affairs Training Center, the FSI provides more than 600 courses in approximately 70 foreign languages to more than 100,000 enrollees a year from the State Department and more than 40 other government agencies and the military service branches.

Organized like a university, it consists of five schools: The School of Language Studies, the School of Applied Information Technology, The School of Leadership and Management, The School of Professional and Area Studies and The Transition Center. 

The FSI has sorted non-English languages into three categories based on the average time it takes an English speaker to achieve general proficiency/fluency in the language.

Category I languages : These languages are the most similar to English and the least difficult to learn, requiring anywhere from 23-24 weeks to learn (Spanish) to 30-36 weeks to learn (German).

Examples are:

French, Italian, Spanish, Swedish, Portuguese, Danish, Catalan, Dutch, Norwegian, German

Category II languages: These languages contain significant linguistic or culture differences from English requiring 44 or more weeks to learn.

Examples are:

Greek, Hebrew, Hindi, Polish, Russian, Finnish (which is one of the more difficult Category II languages)

Category III languages: These languages are considered the most difficult languages to learn, requiring about 88 weeks of study with about half of that time studying in-country.

These languages are:
Arabic, Cantonese, Japanese, Korean, Mandarin, Taiwanese and Wu.