In the previous section, a mathematical expression was defined as some arithmetic combination of numbers, operators, and variables.
A mathematical equation is simply two mathematical expressions joined
by an equals sign (=). An equation is a statement or assertion that its
two expressions are equivalent.

The equations that are created will fall into one of the following
categories. The category they belong to determines how they are
handled:

It has already been shown that the "Anything else?" prompt can be followed by user input that can further define the current problem, or "No" when there is nothing else to add...

What has not been shown is how the "Anything else?" prompt can lead to contradictory input or follow-up questions which become longer passages of discourse. The interaction between separate pieces of input, and how they form dialogues, is the topic of the next section.