It is, in fact, called an expression. To be more precise, an algebraic expression.
An expression.
Expression
A variable expression includes variables.
Algebraic expression
That sounds like the definition for Recursive Formula.
What are the choices?
It is a bigger expression.
They are terms of an expression or an equation
The difference between these two is that an expression only contains variables, numbers, and mathematical symbols, and an equation contains two expression with an equal sign that separate them. For example, while an expression is "2x-1", an equation is "2x-1 = 5x."
It is an expression.
Expression
It is an expression.