near synonym: a term that represents the same or a very similar concept as another term in the same language, but for which interchangeability is limited to some contexts and inapplicable in others
logical expression: an expression used to represent a concept based on mathematical or logical relations, such as statements of inequality, set relationships, boolean operations, and the like
equation: an expression used to represent a concept based on a statement that two mathematical expressions are, for instance, equal as identified by the equal sign (=), or assigned to one another by a similar sign