Absolute Quota
Quotas that permit a limited number of units of specified merchandise to be entered or withdrawn for consumption during specified periods.
Ad Valorem
Duty imposed on imported merchandise based on a percentage of the value.  Lating for according to value.
African Growth & Opportunity Act (AGOA)
The AGOA provides for the duty free entry of certain non-textile articles previously excluded from preferential treatment under the Generalized System of Preferences program, as well as duty-free and quota-free entry of certain textile and apparel articles which meet certain specific production requirements. 
Air Waybill
A non-negotialbe bill of lading , which covers both domestic and international, flights and serves as a contract for carriage.  The document serves as a receipt for the shipper, indicating that the carrier has accepted the goods listed and obligates the carrier to take the merchandise to the airport of destination according to specified conditions.
Antidumping Duty:
Additional duties assessed against a product found by the International Trade Commission to be sold at less than fair value to importers in the U.S. "Dumping" occurs when a foreign vendor or manufacturer sells the product in the U.S. for less than its cost of production or less than the sale price in the home market.
Export Control Classification Number (ECCN)
ECCN, stands for Export Control Classification Number. An ECCN is an alpha-numeric classification used in the Commerce Control List to identify items for export control purposes. An ECCN is different from a Schedule B number, which is used by the Bureau of Census to collect trade statistics. It is also different from the Harmonized Tariff System Nomenclature, which is used to determine import duties.

All ECCNs will have 5 characters, for example, 1A001, 4B994, or 8D001. There are 10 categories on the Commerce Control List. The first number of the ECCN identifies the category to which it belongs, for example, 1 = Nuclear Materials Facilities and Equipment, 4 = Computers, 9 = Propulsion Systems, Space Vehicles and Related Equipment.

However, EAR99 is a different type of classification. It serves as a "basket" designation for items that are covered by the EAR, but are not specified on the Commerce Control List. EAR99 items can be shipped without a license to most destinations under most circumstances. There are limitations on the use of EAR99. However, the majority of the commercial exports from the United States fall into this category.

United States Munitions List (USML)

The United States Munitions List (USML) is a list of articles, services, and related technology designated as defense-related by the United States federal government. This designation is pursuant to sections 38 and 47(7) of the Arms Export Control Act (22 U.S.C. 2778 and 2794(7)). These articles fall under the export and temporary import jurisdiction of the Department of State.

The USML is found in Part 121 of Title 22, Foreign Relations, of the Code of Federal Regulations (CFR). The USML is amended by rules published in the Federal Register. Further information and clarification whether specific articles or services fall under the USML are periodically discussed in Defense Trade News published by the State Department's Bureau of Political-Military Affairs.

Any article, service, or related data found to be on the USML requires an export license (issued by the United States State Department) to be exported (given to a non-U.S. person). A "U.S. person" is a U.S. citizen or permanent resident who does not work for a foreign company, government, or NGO. Some license exceptions are available under specific circumstances.

Harmonized Tariff Code(HTS) 

The Harmonized Tariff Schedule of the United States (HTS) was enacted by Congress and made effective on January 1, 1989, replacing the former Tariff Schedules of the United States.

The HTS comprises a hierarchical structure for describing all goods in trade for duty, quota, and statistical purposes. This structure is based upon the international Harmonized Commodity Description and Coding System (HS), administered by the World Customs Organization in Brussels ; the 4- and 6-digit HS product categories are subdivided into 8-digit unique U.S. rate lines and 10-digit non-legal statistical reporting categories. Classification of goods in this system must be done in accordance with the General and Additional U.S. Rules of Interpretation, starting at the 4-digit heading level to find the most specific provision and then moving to the subordinate categories.

The "general" rates of duty subcolumn contains U.S. normal trade relations duty rates; products of some NTR countries may be eligible for preferential tariff programs, as reflected in the "special" subcolumn. Column 2 (the so-called "statutory rates") applies to countries listed in general note 3(b); the general notes set forth the rules for applying the HTS. Embargoes, anti-dumping duties, countervailing duties, and other very specific matters administered by the Executive Branch are not contained in the HTS.

The USITC maintains and publishes the HTS (in print and on-line) pursuant to the Omnibus Trade and Competitiveness Act of 1988; see the preface to the HTS for additional explanatory material. However, the Bureau of Customs and Border Protection of the Department of Homeland Security is responsible for interpreting and enforcing the HTS.