It's usually referred to as an "expression."
a equation
a number sentence contains an equal sign
The answer, the solution.
An equation.
a number sentence.
a equation
Is a number sentence that does not equal anything or has an equal sign.
Equation
a number sentence contains an equal sign
A number sentence that equals or that has an equal sign.
The answer, the solution.
An equation.
a number sentence.
EQUATION
5+101=106
a variable expression
7 x 8 is not a number sentence because it does not have an equal sign (=) and it does not have a solution.