Many global problems, such as global warming, lack of natural resources, wars and famine, happen in one country, but will influence other countries. In economic realm, consider that a financial crisis—or a political crisis or natural disaster in one country can spell trouble for foreign companies, many of which are now multinational in that they rely on labor forces, equipment, and raw materials of other nations. Also, international cooperation is evident in the realm of inhibiting and fighting against the crimes such as international drug transaction and terrorism.
2、 其他
4) Several years ago, it was reported that the Gross National Income of 7 African nations was less than
one big firm in the United States.
5) 语言学家linguists预测，每两个星期，将有一种语言在世界某个地方消亡。
6) 国家之间通过正式的方式：外交关系diplomatic relations、军事和经济同盟military and economic alliances、全球化组织global organizations如联合国等链接。
也可以通过非正式方式：文化交流cultural exchanges、游客tourists、交换学生students exchanges、国际贸易international trade和非政府组织nongovernment organizations
