Definition:Proposition

Definition
A proposition is a statement which is offered up for investigation as to its truth or falsehood.

Loosely, a proposition is a statement which is about to be proved (or disproved).

Also defined as
Some sources, while appreciating the need under certain circumstances to do so, do not distinguish between the concept of a statement, as defined here on, and a proposition, using the terms interchangeably:
 * "There are good reasons, which fortunately we do not need to go into, for avoiding the term 'proposition'. On the other hand, we shall, in the early sections of this book, be working with what is known as the Propositional Calculus. We shall use the terms 'statement' and 'proposition' interchangeably."
 * $\S 1.1$