She looked at him curiously - at his ugly tweed suit, his yellow boots, and up into the strong, forceful face with eyes set in deep hollows under his protruding brows, at the heavy jaws giving a certain coarseness to his expression, which his mouth and forehead, well-shaped though they were, could not altogether dispel.
Definition of Expression. An Expression is a mathematical phrase that combines numbers and/or variables using mathematical operations. An expression is a representation of a value; for example, variables and/or numerals that appear alone or in combination with operators are expressions.
Equations are commonly used in mathematics and chemistry. A mathematical equation is a statement that asserts that two different expressions are equal. The expressions are usually separated by an equals sign to show that one side balances the other.A chemical equation is a formula for showing a chemical reaction.