equation

equation /equa·tion/ (e-kwa´zhun) an expression of equality between two parts.

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Henderson-Hasselbalch equation  a formula for calculating the pH of a buffer solution such as blood plasma.

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e·qua·tion (-kwzhn)

n.

1. A statement asserting the equality of two mathematical expressions, usually written as a linear array of symbols that are separated into left and right sides and are joined by an equal sign.

2. A representation of a chemical reaction, usually written as a linear array in which the symbols and quantities of the reactants are separated from those of the products by an equal sign, arrow, or set of opposing arrows.