The crossword solution for the term BASE'S COUNTERPART is ACID. An ACID is a substance that has a sour taste and reacts with metals to form salts. Acids are also known for their corrosive properties, which can cause damage to materials such as wood, metal, and stone. Acids are typically classified as either mineral acids or organic acids, depending on their chemical composition. The base counterpart to an ACID is a base, which is a substance that neutralizes acids and has a bitter taste. Bases are also known for their alkaline properties, which can be used to neutralize acids and other substances.