The WTO recognizes as least-least developed (LDCs) those countries which have been designated as such by the United Nations:

Afghanistan, Angola, Bangladesh, Benin, Bhutan, Burkina Faso, Burundi, Cambodia, Cape Verde, Central African Republic, Chad, Comoros, Democratic Republic of the Congo, Djibouti, East Timor, Equatorial Guinea, Eritrea, Ethiopia, Gambia, Guinea, Guinea-Bissau, Haiti, Kiribati, Lao People's Democratic Republic, Lesotho, Liberia, Madagascar, Malawi, Maldives, Mali, Mauritania, Mozambique, Myanmar, Nepal, Niger, Rwanda, Samoa, Sao Tome and Principe, Senegal, Sierra Leone, Solomon Islands, Somalia, Sudan, Tanzania, Togo, Tuvalu, Uganda, Vanuatu, Yemen and Zambia.

In some Members' markets, Least Developed Countries are accorded a preferential treatment more favourable than GSP (in general duty-free treatment with no limitations). See also ENABLING CLAUSE.

See DUTY.

To assess or impose a tariff on imported merchandise (when used as a verb), or the charge on imports (when used as a noun).   

Source: http://www.asycuda.org/cuglossa.asp?firstlet=L&submit1=Browse

Unilateral or multilateral reductions in tariffs and other measures that restrict trade. Trade liberalization has been the objective of all rounds of the GATT trade negotiations.

Source: http://usinfo.state.gov/products/pubs/trade/glossjr.htm#j

The requirement by a country of making formal application for a special permit, usually called a "license," as a prior condition for importing or exporting certain goods.

Source: http://usinfo.state.gov/products/pubs/trade/glossjr.htm#licensing

A Tokyo Round code aimed at simplifying import licensing procedures and at ensuring their fair and equitable application. The code also seeks to improve the transparency of such proceedings by requiring the publication of relevant national laws and regulations. A Committee on Import Licensing, under the aegis of GATT, monitored adherence to the code. The WTO Agreement on Import Licensing Procedures, negotiated during the Uruguay Round, is the successor to the Licensing Code.  

Source: http://usinfo.state.gov/products/pubs/trade/glossjr.htm#j

Negotiation modality in which it is agreed that a reduction is made by a given percentage in all tariffs maintained by countries participating in a round of trade negotiations, with or without exceptions for products deemed to be "sensitive." It is sometimes called "horizontal reduction of tariffs," "across-the-board reduction of tariffs," or "equal percentage reduction of tariffs."  

Derived from: http://usinfo.state.gov/products/pubs/trade/glossjr.htm#linred

See SCHEDULES.