A formula is a sentence containing variables. Formulas often describe a relation between those variables, but not always.
Formulas often look like an equation, i.e. a sentence with an equals sign.
If a formula describes a relation between two variables, you can draw a corresponding graph. First, you make a table. Next you draw the points in a coordinate system and connect them.
In practice, formulas often describe relationships between quantities. Those quantities are represented by a variable, a letter which corresponds to the
name of the quantitiy used.
A quantity is measured in units.
The formula is an equation defining the relation between the variables and . You can make the corresponding table and plot the corresponding graph.
The formula gives information about the unknown . The solution to this equation is , for .
The formula is a calculation rule and is valid for all .