American (word) ("United States person"), which derives from ' ("United States of America"). The Spanish term ' ("North American") is frequently used to refer things and persons from the United States, but this term can also denote people and things from Canada and Mexico. Among Spanish-speakers, North America generally doesn't include Central America or the Caribbean. In other languages, however, there is no possibility for confusion. For example, the Chinese word for "U.S. national" is ' () is derived from a word for the United States, ', where ' is an abbreviation for "Yàměilìjiā" ("America") and ' is "country". The name for
Word problem for groups would expect it to be difficult to prove as the mapping from presentations to simple groups would have to be non-recursive. The following has been proved by Bernhard Neumann and Angus Macintyre: What is remarkable about this is that the algebraically closed groups are so wild that none of them has a recursive presentation. The oldest result relating algebraic structure to solvability of the word problem is Kuznetsov's theorem: To prove this let ⟨"X"|"R"⟩ be a recursive presentation for "S". Choose "a" ∈ S such that "a" ≠ 1 in "S". If "w" is a word on the generators "X"