"Standard form" is a general term used in mathematics to refer to a normalized form of an expression. The term "canonical form" is also used in certain contexts (for example, graphs).
The standard form of a line in the Cartesian plane is given by
(1)

for real numbers .
This form can be derived from any of the other forms (pointslope form, slopeintercept form, etc.), but can be seen most intuitively when starting from intercept form. Indeed, the intercept form of a line with xintercept and yintercept is given by
(2)

and so clearing denominators to obtain
(3)

gives the line in standard form with , , and .