What is the difference between dry powder extinguisher and dry chemical fire extinguisher?

The terms "dry powder" and "dry chemical", is used in regards to fire protection, refering to extinguishing agents.

Civilians, Lay persons and non-fire protection specialists use the terms interchangably. To be exact however, Dry Chemical refers to agents that extinguish Class A, B and C type fires, while Dry Powders refer to agents that extinguish Class-D type fires. Dry Chemicals have the consistancy of a flour like substance. Dry Powders have the consistancy of salt like substances. The difference is obvious to fire service professionals but not so for those who do not come in contact with the substances very often. Even the National Fire Protection Association confuses the issue when they use the Word "powder" in their definition of a dry chemical.

NFPA 17 defines a dry chemical as: "a powder composed of very small particles, usually sodium bicarbonate, potassium bicarbonate, or ammonium phosphate-based with added particulate material supplemented by special treatment to provide resistance to packing, resistance to moisture absorption (caking), and the proper flow capabilities."